WinForms XML - Stellar Water Point

Application Setup

Introduction

Hi, for our exercise, we will create a text-based database Windows Forms application. We will us XML to store the records of our database.

Practical Learning: Introducing the Application

Start Microsoft Visual Studio
In the Visual Studion 2022 dialog box, click Create a New Project
In the Create a New Project dialog box, in the languages combo box, select C#.
In the list of projects templates, click Windows Forms App
Click Next
Change the Project Name to StellarWaterPoint1.
Set the Location to a path of your choice
Click Next
In the Additional Information wizard page, in the Framework combo box, select the highest version (.NET 9.0 (Standard Term Support)
Click Create

The Main Form of the Application

Our application will use a central form to access the other form. We will use the default form for that purpose. Our application will use records for water meters, customers, and water bills. Therefore, we will add some buttons for the forms related to those records.

Practical Learning: Preparing the Central Form of the Application

In the Solution Explorer, right-click Form1.cs and click Rename
Type WaterDistribution (to get WaterDistribution.cs) and press Enter
Read the message on the message box and click Yes
Click the body of the form to make sure it is selected.
In the Properties window, change the following characteristics:
Text: Stellar Water Point
StartPosition: CenterScreen
MaximizeBox: False
Double-click an unoccupied area of the form to generate its Load event

Impliment the event as follows:

namespace StellarWaterPoint
{
    public partial class WaterDistribution : Form
    {
        public WaterDistribution()
        {
            InitializeComponent();
        }

        private void WaterDistribution_Load(object sender, EventArgs e)
        {
            // If the directory for the database doesn't yet exist, create it
            Directory.CreateDirectory(@"C:\Stellar Water Point");
        }
    }
}

Water Meters

Introduction

Our application will use forms to create water meter records, to view a record of a water meter, to edit or to delete the record of a water meter.

Practical Learning: Introducing Water Meters

To create a folder, in the Solution Explorer, right-click the StellarWaterPoint1 project -> Add -> New Folder
Type WaterMeters as the name of the folder

Displaying Water Meters

To let the user see a list of the water meters in the database, we will use a form equipped with a list view.

Practical Learning: Displaying Water Meters

To create a form, in the Solution Explorer, right-click WaterMeters -> Add -> Form (Windows Forms)...
TFor the Name of the form, type Central
Click Add
In the Toolbox, click the ListView button and click the form
On the form, right-click the list view and click Edit Columns...

Create the columns as follows:

(Name)	Text	Width
colWaterMeterId	Id	40
colMeterNumber	Meter #	150
colMake	Make	300
colModel	Model	150
colMeterSize	Meter Size	150

Click OK

Position and resize the list view on the form as follows:

Control		(Name)	Other Properties
ListView		lvwWaterMeters	FullRowSelect: True GridLines: True View: Details Anchor: Top, Bottom, Left, Right

Doubte-click an unoccupied area of the form to generate its Load event

Change the document as follows:

using System.Xml;

namespace StellarWaterPoint1.WaterMeters
{
    public partial class Central : Form
    {
        public Central()
        {
            InitializeComponent();
        }
        private void ShowWaterMeters()
        {
            // Create a reference to the XML's DOM object
            XmlDocument xdWaterMeters = new XmlDocument();
            // Indicate the file that holds a list of water meters
            string strFileWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";

            // Check whether a file that holds a list of water meters exists
            if(File.Exists(strFileWaterMeters))
            {
                // If that file exists, open it
                using (FileStream fsWaterMeters = new FileStream(strFileWaterMeters, FileMode.Open,
                                                                 FileAccess.Read, FileShare.Read))
                {
                    /* Get the list of water meters from the file and store
                     * the records in the previously created DOM object. */
                    xdWaterMeters.Load(fsWaterMeters);

                    /* If there is at least one record for the water meters, 
                     * create an XmlNodeList list and transmit it to 
                     * a ViewData collection that wille be used in the view page.*/
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.ChildNodes;

                    int id = 1;

                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        ListViewItem lviWaterMeter = new ListViewItem(id++.ToString());

                        lviWaterMeter.SubItems.Add(xnWaterMeter.FirstChild!.InnerText);
                        lviWaterMeter.SubItems.Add(xnWaterMeter.FirstChild.NextSibling!.InnerText);
                        lviWaterMeter.SubItems.Add(xnWaterMeter.FirstChild.NextSibling.NextSibling!.InnerText);
                        lviWaterMeter.SubItems.Add(xnWaterMeter.FirstChild.NextSibling.NextSibling.NextSibling!.InnerText);

                        lvwWaterMeters.Items.Add(lviWaterMeter);
                    }
                }
            }
        }

        private void Central_Load(object sender, EventArgs e)
        {
            ShowWaterMeters();
        }
    }
}

In the Solution Explorer, double-click WaterDistribution.cs to display the main form of the application
From the Toolbox, add a button to the form

From the Properties window, change the characteristics of the button as follows:

Control		(Name)	Text	Font
Button		btnWaterMeters	&Water Meters...	Times New Roman, 24pt, style=Bold

Double-click the &Water Meters button

Impliment the event as follows:

namespace StellarWaterPoint1
{
    public partial class WaterDistribution : Form
    {
        public WaterDistribution()
        {
            InitializeComponent();
        }

        private void WaterDistribution_Load(object sender, EventArgs e)
        {
            // If the directory for the database doesn't yet exist, create it
            Directory.CreateDirectory(@"C:\Stellar Water Point");
        }

        private void btnWaterMeters_Click(object sender, EventArgs e)
        {
            WaterMeters.Central central = new WaterMeters.Central();

            central.ShowDialog();
        }
    }
}

A Water Meter Record

Our application will have a list of water meters. A record for each water meter must be created. To make this happen, we will equip the application with an appropriate form.

Practical Learning: Creating a Water Meter Record

To create a form, in the Solution Explorer, right-click the WaterMeters folder -> Add -> Form (Windows Forms)...
For the Name of the file, type Create as the name of the form
Click Add

Design the form as follows:

Stellar Water Point - New Water Meter

Control	(Name)	Text	Other Properties
Label		&Meter #:
MaskedTextBox	mtbMeterNumber		Masked: 000-000-000
Label		M&ake:
TextBox	txtMake		Modifiers: Public
Label		M&odel:
TextBox	txtModel		Modifiers: Public
Label		Me&ter Size:
TextBox	txtMeterSize		Modifiers: Public
Button	btnOK	&OK	DialogResult: OK
Button	btnCancel	&Cancel	DialogResult: Cancel

Using the Properties window, change some characteristics of the form as follows:

FormBorderStyle: FixedDialog
Text:            Stellar Water Point - Water Meter Setup
StartPosition:   CenterScreen
AcceptButton:    btnOK
CancelButton:    btnCancel

In the Solution Explorer, below the WaterMeters folder, double-click Central.cs
From the Toolbox, add a button to the form below the list view

Change the characteristics of the button as follows:

Control	(Name)	Other Properties
ListView	lvwWaterMeters	FullRowSelect: True GridLines: True View: Details Anchor: Top, Bottom, Left, Right
Button	btnNewWaterMeter	&New Water Meter... Anchor: Bottom, Right

On the Central form, double-click the New Water Meter button

Implement the event as follows:

using System.Xml;

namespace StellarWaterPoint10.WaterMeters
{
    public partial class Central : Form
    {
        public Central()
        {
            InitializeComponent();
        }

        private void ShowWaterMeters()
        {
            // Create an XML Dom reference
            XmlDocument xdWaterMeters = new XmlDocument();
            // Declare a string variable to have the file that holds a list of water meters
            string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";

            // Create a FileInfo object that holds a reference to the file of water meters
            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            // If you are about to display a list of water meters, first empty the list view
            lvwWaterMeters.Items.Clear();

            // Check whether a file for water meters was previously created.
            if (fiWaterMeters.Exists)
            {
                // If such a file exists, create a Stream for it
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    // Store the stream of water meters into the XML Dom that was created earlier
                    xdWaterMeters.Load(fsWaterMeters);
                    // Get a list of the water meter elements from the XML Dom object
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.ChildNodes;

                    int i = 1;

                    lvwWaterMeters.Items.Clear();

                    // Check each water meter
                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        // Create a list view item to hold a record of a water meter
                        ListViewItem lviWaterMeter = new ListViewItem(i.ToString());

                        lviWaterMeter.SubItems.Add(xnWaterMeter.FirstChild!.InnerText);
                        lviWaterMeter.SubItems.Add(xnWaterMeter.FirstChild.NextSibling!.InnerText);
                        lviWaterMeter.SubItems.Add(xnWaterMeter.FirstChild.NextSibling.NextSibling!.InnerText);
                        lviWaterMeter.SubItems.Add(xnWaterMeter.FirstChild.NextSibling.NextSibling.NextSibling!.InnerText);

                        // Pass the list view item to the list view object on the form
                        lvwWaterMeters.Items.Add(lviWaterMeter);

                        i++;
                    }
                }
            }
        }

        private void Central_Load(object sender, EventArgs e)
        {
            // When the open opens, make an attempt to display a list of water meters.
            ShowWaterMeters();
        }

        private void btnNewWaterMeter_Click(object sender, EventArgs e)
        {
            // Get a reference to the form used to add a water meter
            Create wm = new();
            // Create a FileInfo object
            FileInfo? fiWaterMeters = null;
            // Create a file stream object
            FileStream? fsWaterMeters = null;
            // Create an XML Dom object
            XmlDocument xdWaterMeters = new XmlDocument();
            // Declare a string for a file to hold a list of water meters
            string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";

            /* Display the form used to create a water meter. 
             * If the user finishes using that form and click the OK button... */
            if (wm.ShowDialog() == DialogResult.OK)
            {
                // Store the file of water meters into the FileInfo object that was previously created.
                fiWaterMeters = new FileInfo(strWaterMeters);

                /* Find out whether a list of water meters was previously created 
                 * and was stored in the string file declared above. */
                if (fiWaterMeters.Exists)
                {
                    /* If that file exists already, create a Stream object 
                     * for it with a read-only status. */
                    using (fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open,
                                                          FileAccess.Read, FileShare.Read))
                    {
                        // Pass the list of water meters to the XML Dom object created earlier
                        xdWaterMeters.Load(fsWaterMeters);
                    }
                }
                else
                {
                    // If a file for water meters was not previously created, create it now...
                    using (fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Create,
                                                          FileAccess.Write, FileShare.Write))
                    {
                        // and create the root XML element for it
                        xdWaterMeters.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                                              "<water-meters></water-meters>");
                        // Make sure you save the new file
                        xdWaterMeters.Save(fsWaterMeters);
                    }
                }

                // Now that the file exists, open it
                using (fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.OpenOrCreate, 
                                                      FileAccess.ReadWrite, FileShare.ReadWrite))
                {
                    // Start creating a new Water Meter XML element
                    XmlElement xeWaterMeter = xdWaterMeters.CreateElement("water-meter");

                    /* Use the values that the user had typed in the Create form.
                     * Use those values to create the child elements of the new water meter node.
                     * Assign the combination of child elements to the new water meter node. */
                    xeWaterMeter.InnerXml = "<meter-number>" + wm.mtbMeterNumber.Text + "</meter-number>" +
                                            "<make>" + wm.txtMake.Text + "</make>" +
                                            "<model>" + wm.txtModel.Text + "</model>" +
                                            "<meter-size>" + wm.txtMeterSize.Text + "</meter-size>";
                    // Once the XML element is ready, add/append it to the XML Dom that was previously created.
                    xdWaterMeters.DocumentElement!.AppendChild(xeWaterMeter);
                    // Once the new element has been created and add it to the file, save that file
                    xdWaterMeters.Save(fsWaterMeters);
                }
            }

            /* Whenever the user has finished using the Create form, 
             * make an attempt to display the list of water meters. */
            ShowWaterMeters();
        }
    }
}

To execute the application, on the main menu, click Debug -> Start Without Debugging
On the Central form, click the Water Meters button:
Click the New Water Meter button:

Enter the value for each of the following records and click OK (or press Enter) for each:

Meter #	Make	Model	Meter Size
392-494-572	Constance Technologies	TG-4822	5/8 Inches
938-705-869	Stan Wood	66-G	1 Inch
588-279-663	Estellano	NCF-226	3/4 Inches

Close the forms and return to your programming environment

Water Meter Details

Once a database exists, sometimes a use mmay want to check the values of a water meter record. To support this, we will add an appropriate form to our application.

Practical Learning: Creating a Water Meter Record

To create a form, in the Solution Explorer, right-click WaterMeters -> Add -> Form (Windows Forms)...
For the Name of the form, type Details
Press Enter
Resize the Editor form to have the same size as the Create form
Copy everything from the Create form and paste it in the Editor form
Delete the bottom two buttons and add a new button

Change the design of the form as follows:

Stellar Water Point - New Water Meter

Control	(Name)	Text
Button	btnFindWateMeter	&Find Water Meter
Button	btnClose	&Close

On the form, double-click the Find button
Return to the form and double-click the Close button

Change the document as follows:

using System.Xml;

namespace StellarWaterPoint10.WaterMeters
{
    public partial class Details : Form
    {
        public Details()
        {
            InitializeComponent();
        }

        private void btnFindWateMeter_Click(object sender, EventArgs e)
        {
            /* If the user clicks the Find button, 
             * make sure there is a meter number in the top text box. */
            if (string.IsNullOrEmpty(mtbMeterNumber.Text))
            {
                /* If the user didn't type a meter number, 
                 * display a message box to inform the user. */
                MessageBox.Show("You must type a meter number and then click the Find button.",
                                "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
                // If the user didn't type a meter number but clicked Find, don't do anything
                return;
            }

            // We will need a reference to an XML Dom object as an XmlDocument variable
            XmlDocument xdWaterMeters = new XmlDocument();
            // This is the name and path of the file that holds the records of water meters
            string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
            // We will process the file of water meters using a FileInfo object
            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            // We need to find out whether a file for water meters was previously created.
            if (fiWaterMeters.Exists)
            {
                // If that file exists, create a stream of it. Open that file with a read-only status
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    // Get the list of water meter records and put those records in the XML Dom object created earlier.
                    xdWaterMeters.Load(fsWaterMeters);
                    /* Use XPath to locate the water meter that has 
                     * the same meter number as the one in the Meter # text box.
                     * Store the water meter in an XmlNodeList variable. */
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + mtbMeterNumber.Text + "']")!;

                    /* If there is a water meter in the database with 
                     * the number that the user typed, locate that water meter 
                     * and display each of its values in the appropriate text box. */
                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        txtMake.Text = xnWaterMeter.NextSibling!.InnerText;
                        txtModel.Text = xnWaterMeter.NextSibling.NextSibling!.InnerText;
                        txtMeterSize.Text = xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText;
                    }
                }
            }
        }

        private void btnClose_Click(object sender, EventArgs e)
        {
            Close();
        }
    }
}

In the Solution Explorer, below the WaterMeters folder, double-click Central.cs to open its form
On the form, click the list view
In the Properties window, click the Events button
In the Events section of the Properties window, double-click DoubleClick

Implement the event as follows:

using System.Xml;

namespace StellarWaterPoint3.WaterMeters
{
    public partial class Central : Form
    {
        public Central()
        {
            InitializeComponent();
        }
        
        . . .

        private void lvwWaterMeters_DoubleClick(object sender, EventArgs e)
        {
            if(lvwWaterMeters.SelectedItems.Count > 0)
            {
                Details details = new();

                details.mtbMeterNumber.Text = lvwWaterMeters.SelectedItems[0].SubItems[1].Text;

                XmlDocument xdWaterMeters = new XmlDocument();
                string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
                FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

                if (fiWaterMeters.Exists)
                {
                    using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdWaterMeters.Load(fsWaterMeters);
                        XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + lvwWaterMeters.SelectedItems[0].SubItems[1].Text + "']")!;

                        foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                        {
                            details.txtMake.Text = xnWaterMeter.NextSibling!.InnerText;
                            details.txtModel.Text = xnWaterMeter.NextSibling.NextSibling!.InnerText;
                            details.txtMeterSize.Text = xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText;
                        }
                    }
                }

                details.ShowDialog();
            }
        }
    }
}

Return to the form
From the Toolbox, add a button to the form below the list view and to the right of the New Water Meter button

Change the characteristics of the button as follows:

Control	(Name)	Other Properties
ListView	lvwWaterMeters	No Change
Button	btnNewWaterMeter	&New Water Meter... Anchor: Bottom, Right
Button	btnViewWaterMeter	&View Water Meter... Anchor: Bottom, Right

Double-click the View Water Meter button

Change the document as follows:

using System.Xml;

namespace StellarWaterPoint1.WaterMeters
{
    public partial class Central : Form
    {
        public Central()
        {
            InitializeComponent();
        }

        private void ShowWaterMeters()
        {
            . . .
        }

        private void Central_Load(object sender, EventArgs e)
        {
            // When the open opens, make an attempt to display a list of water meters.
            ShowWaterMeters();
        }

        private void btnNewWaterMeter_Click(object sender, EventArgs e)
        {
            . . .
        }

        private void lvwWaterMeters_DoubleClick(object sender, EventArgs e)
        {
            if(lvwWaterMeters.SelectedItems.Count > 0)
            {
                Details details = new();

                details.mtbMeterNumber.Text = lvwWaterMeters.SelectedItems[0].SubItems[1].Text;

                XmlDocument xdWaterMeters = new XmlDocument();
                string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
                FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

                if (fiWaterMeters.Exists)
                {
                    using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdWaterMeters.Load(fsWaterMeters);
                        XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + lvwWaterMeters.SelectedItems[0].SubItems[1].Text + "']")!;

                        foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                        {
                            details.txtMake.Text = xnWaterMeter.NextSibling!.InnerText;
                            details.txtModel.Text = xnWaterMeter.NextSibling.NextSibling!.InnerText;
                            details.txtMeterSize.Text = xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText;
                        }
                    }
                }

                details.ShowDialog();
            }
        }

        private void btnViewWaterMeter_Click(object sender, EventArgs e)
        {
            /* Get a reference to the dialog box that is used 
             * to view information about a water meter. */
            Details view = new();
            // Display that dialog box
            view.ShowDialog();

            // After using the dialog box, make an attempt to display the list of water meters.
            ShowWaterMeters();
        }
    }
}

To execute the application, on the main menu, click Debug -> Start Without Debugging
On the Water Distribution form, click the Water Meters button
On the Central form of water meters, click the View Water Meter button:
In the Meter # text, type 392-494-572
Click the Find button:
Close the Details form
On the Water Meters form, double-click the third record
Close the forms and return to your programming environment

Updating a Water Meter Details

One of the routine operations performed on a database is to change the details of a record. To support this operation for a water meter, we will create a form that can be used to update the information of a water meter.

Practical Learning: Updating a Water Meter

To create a form, in the Solution Explorer, right-click WaterMeters -> Add -> Form (Windows Forms)...
For the Name of the file, type Editor as the name of the form
Click Add
Resize the Editor form to have the same size as the Details form
Copy everything from the Details form and paste it in the Editor form

Change the design of the form as follows:

Stellar Water Point - New Water Meter

Control		(Name)	Text
Button		btnUpdateWateMeter	&Update Water Meter

On the form, double-click the Find button

Change the document as follows:

using System.Xml;

namespace StellarWaterPoint1.WaterMeters
{
    public partial class Editor : Form
    {
        public Editor()
        {
            InitializeComponent();
        }

        private void btnFind_Click(object sender, EventArgs e)
        {
            XmlDocument xdWaterMeters = new XmlDocument();
            string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";

            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            if (fiWaterMeters.Exists)
            {
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterMeters.Load(fsWaterMeters);
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + mtbMeterNumber.Text + "']")!;

                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        txtMake.Text = xnWaterMeter.NextSibling!.InnerText;
                        txtModel.Text = xnWaterMeter.NextSibling.NextSibling!.InnerText;
                        txtMeterSize.Text = xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText;
                    }
                }
            }
        }
    }
}

Return to the form and double-click the Update Water Meter button

Change the document as follows:

using System.Xml;

namespace StellarWaterPoint1.WaterMeters
{
    public partial class Editor : Form
    {
        public Editor()
        {
            InitializeComponent();
        }

        . . .

        private void btnUpdateWaterMeter_Click(object sender, EventArgs e)
        {
            XmlDocument xdWaterMeters = new XmlDocument();
            string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";

            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            if (fiWaterMeters.Exists)
            {
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterMeters.Load(fsWaterMeters);
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + mtbMeterNumber.Text + "']")!;

                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        xnWaterMeter.ParentNode!.InnerXml = "<meter-number>" + mtbMeterNumber.Text + "</meter-number>" +
                                                            "<make>" + txtMake.Text + "</make>" +
                                                            "<model>" + txtModel.Text + "</model>" +
                                                            "<meter-size>" + txtMeterSize.Text + "</meter-size>";
                    }
                }

                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite))
                {
                    xdWaterMeters.Save(fsWaterMeters);
                }
            }

            Close();
        }
    }
}

Return to the form and double-click the Close button

Change the document as follows:

using System.Xml;

namespace StellarWaterPoint10.WaterMeters
{
    public partial class Editor : Form
    {
        public Editor()
        {
            InitializeComponent();
        }

        private void btnFindWateMeter_Click(object sender, EventArgs e)
        {
            /* If the user clicks the Find button, 
             * make sure there is a meter number in the top text box. */
            if (string.IsNullOrEmpty(mtbMeterNumber.Text))
            {
                /* If the user didn't type a meter number, 
                 * display a message box to inform the user. */
                MessageBox.Show("You must type a meter number and then click the Find button.",
                                "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
                // If the user didn't type a meter number but clicked Find, don't do anything
                return;
            }

            // We will need a reference to an XML Dom object as an XmlDocument variable
            XmlDocument xdWaterMeters = new XmlDocument();
            // This is the name and path of the file that holds the records of water meters
            string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
            // We will process the file of water meters using a FileInfo object
            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            // We need to find out whether a file for water meters was previously created.
            if (fiWaterMeters.Exists)
            {
                // If that file exists, create a stream of it. Open that file with a read-only status
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    /* Get the list of water meter records 
                     * and put those records in the XML Dom object created earlier. */
                    xdWaterMeters.Load(fsWaterMeters);
                    /* Use XPath to locate the water meter that has 
                     * the same meter number as the one in the Meter # text box.
                     * Store the water meter in an XmlNodeList variable. */
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + mtbMeterNumber.Text + "']")!;

                    /* If there is a water meter in the database with 
                     * the number that the user typed, locate that water meter 
                     * and display each of its values in the appropriate text box. */
                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        txtMake.Text = xnWaterMeter.NextSibling!.InnerText;
                        txtModel.Text = xnWaterMeter.NextSibling.NextSibling!.InnerText;
                        txtMeterSize.Text = xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText;
                    }
                }
            }
        }

        private void btnUpdateWaterMeter_Click(object sender, EventArgs e)
        {
            // We will need a reference to an XML Dom object as an XmlDocument variable
            XmlDocument xdWaterMeters = new();
            // This is the name and path of the file that holds the records of water meters
            string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
            // We will process the file of water meters using a FileInfo object
            FileInfo? fiWaterMeters = new(strWaterMeters);

            // We need to find out whether a file for water meters was previously created.
            if (fiWaterMeters.Exists)
            {
                // If that file exists, create a stream of it. Open that file with a read-only status
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    /* Get the list of water meter records 
                     * and put those records in the XML Dom object created earlier. */
                    xdWaterMeters.Load(fsWaterMeters);
                    /* Use XPath to locate the water meter that has 
                     * the same meter number as the one in the Meter # text box.
                     * Store the water meter in an XmlNodeList variable. */
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + mtbMeterNumber.Text + "']")!;

                    // Check each record of the water meters.
                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        /* If you find a record whose water meter is 
                         * the same as the meter number that the user typed,
                         * change the values of the Make, the Model, 
                         * and the Meter Size based on the values 
                         * the user typed in the corresponding text boxes. */
                        xnWaterMeter.ParentNode!.InnerXml = "<meter-number>" + mtbMeterNumber.Text + "</meter-number>" +
                                                            "<make>" + txtMake.Text + "</make>" +
                                                            "<model>" + txtModel.Text + "</model>" +
                                                            "<meter-size>" + txtMeterSize.Text + "</meter-size>";
                    }
                }

                /* Now that a water meter has been changed/update 
                 * (and the file of water meters has changed), save the new version of the file. */
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite))
                {
                    xdWaterMeters.Save(fsWaterMeters);
                }
            }

            /* If the user has updated a record, we will assume that, 
             * in most cases (such as usually in real life), 
             * a user updates one record and moves to other activities.
             * For this record, after the user has updated a record, 
             * we will clode the form. */
            Close();
        }

        private void btnClose_Click(object sender, EventArgs e)
        {
            Close();
        }
    }
}

In the Solution Explorer, below the WaterMeters folder, double-click Central.cs
From the Toolbox, add a button to the form below the list view and on the right side of the View Water Meter button

Change the characteristics of the button as follows:

Control	(Name)	Other Properties
ListView	lvwWaterMeters	FullRowSelect: True GridLines: True View: Details Anchor: Top, Bottom, Left, Right
Button	btnNewWaterMeter	&New Water Meter... Anchor: Bottom, Right
Button	btnViewWaterMeter	&View Water Meter... Anchor: Bottom, Right
Button	btnEditWaterMeter	&Edit Water Meter... Anchor: Bottom, Right

Display the Central form of the WaterMeters folder
Double-click the Update Water Meter button

Change the document as follows:

using System.Xml;

namespace StellarWaterPoint1.WaterMeters
{
    public partial class Central : Form
    {
        public Central()
        {
            InitializeComponent();
        }

        private void ShowWaterMeters()
        {
            . . .
        }

        private void Central_Load(object sender, EventArgs e)
        {
            // When the open opens, make an attempt to display a list of water meters.
            ShowWaterMeters();
        }

        private void btnNewWaterMeter_Click(object sender, EventArgs e)
        {
            . . .
        }

        private void btnViewWaterMeter_Click(object sender, EventArgs e)
        {
            . . .
        }

        private void btnEditWaterMeter_Click(object sender, EventArgs e)
        {
            /* Get a reference to the dialog box that is used 
             * to update the details of a water meter. */
            Editor editor = new();
            // Display that dialog box
            editor.ShowDialog();

            // After using the dialog box, make an attempt to display the list of water meters.
            ShowWaterMeters();
        }
    }
}

To execute the application, on the main menu, click Debug -> Start Without Debugging
On the Central form, click the Water Meters button
Click the Edit Water Meter button:
In the Meter # text, type 938-705-869
Click the Find button

Change the values as follows:

Make:	Stanford Trend
Model:	266G
Meter Size:	1 1/2 Inches

Stellar Water Point - New Water Meter

Click the Update button:
Close the forms and return to your programming environment

Removing a Water Meter from the Database

If a record is not necessary anymore on a database, the user may want to remove it. To assist the user with this operation, we will create a form withe necessary buttons.

Practical Learning: Deleting a Water Meter Record

To create a form, in the Solution Explorer, right-click WaterMeters -> Add -> Form(Windows Forms)...
In the Name text box, replace the string with Delete as the name of the form
Press Enter
Resize the Delete form to have the same size as the Editor form
Copy everything from the Editor form and paste it in the Delete form

Change the bottom button as follows:

Stellar Water Point - New Water Meter

Control		(Name)	Text
Button		btnDeleteWateMeter	&Delete Water Meter

On the form, double-click the Find Water Meter button

Change the document as tollows:

using System.Xml;

namespace StellarWaterPoint1.WaterMeters
{
    public partial class Delete : Form
    {
        public Delete()
        {
            InitializeComponent();
        }

        private void btnFind_Click(object sender, EventArgs e)
        {
            XmlDocument xdWaterMeters = new XmlDocument();
            string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";

            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            if (fiWaterMeters.Exists)
            {
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterMeters.Load(fsWaterMeters);
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + mtbMeterNumber.Text + "']")!;

                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        txtMake.Text = xnWaterMeter.NextSibling!.InnerText;
                        txtModel.Text = xnWaterMeter.NextSibling.NextSibling!.InnerText;
                        txtMeterSize.Text = xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText;
                    }
                }
            }
        }
    }
}

Return to the form and double-click the Delete Water Meter button

Change the document as tollows:

using System.Xml;

namespace StellarWaterPoint1.WaterMeters
{
    public partial class Delete : Form
    {
        public Delete()
        {
            InitializeComponent();
        }

        . . .

        private void btnDeleteWaterMeter_Click(object sender, EventArgs e)
        {
            XmlDocument xdWaterMeters = new XmlDocument();
            string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";

            if (string.IsNullOrEmpty(mtbMeterNumber.Text))
            {
                MessageBox.Show("You must type a water meter number if you want to delete one.",
                                "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
                return;
            }

            if (!File.Exists(strWaterMeters))
            {
                MessageBox.Show("There is no file for the water meters in the system.",
                                "Stellar Water Point",
                                MessageBoxButtons.OK, MessageBoxIcon.Information);
                return;
            }

            xdWaterMeters.Load(strWaterMeters);

            XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.GetElementsByTagName("meter-number");

            foreach (XmlNode xnWaterMeter in xnlWaterMeters)
            {
                if (xnWaterMeter.InnerText == mtbMeterNumber.Text)
                {
                    if (MessageBox.Show("Are you sure you want to delete this water meter record from the system?",
                                    "Stellar Water Point",
                                    MessageBoxButtons.YesNo, MessageBoxIcon.Question) == DialogResult.Yes)
                    {
                        xdWaterMeters.DocumentElement.RemoveChild(xnWaterMeter.ParentNode!);
                        break;
                    }
                }
            }

            xdWaterMeters.Save(strWaterMeters);

            Close();
        }
    }
}

Return to the form and double-click the Close button

Change the document as tollows:

using System.Xml;

namespace StellarWaterPoint10.WaterMeters
{
    public partial class Delete : Form
    {
        public Delete()
        {
            InitializeComponent();
        }

        private void btnFindWateMeter_Click(object sender, EventArgs e)
        {
            /* If the user clicks the Find button, 
             * make sure there is a meter number in the top text box. */
            if (string.IsNullOrEmpty(mtbMeterNumber.Text))
            {
                /* If the user didn't type a meter number, 
                 * display a message box to inform the user. */
                MessageBox.Show("You must type a meter number and then click the Find button.",
                                "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
                // If the user didn't type a meter number but clicked Find, don't do anything
                return;
            }

            // We will need a reference to an XML Dom object as an XmlDocument variable
            XmlDocument xdWaterMeters = new XmlDocument();
            // This is the name and path of the file that holds the records of water meters
            string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
            // We will process the file of water meters using a FileInfo object
            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            // We need to find out whether a file for water meters was previously created.
            if (fiWaterMeters.Exists)
            {
                // If that file exists, create a stream of it. Open that file with a read-only status
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    /* Get the list of water meter records 
                     * and put those records in the XML Dom object created earlier. */
                    xdWaterMeters.Load(fsWaterMeters);
                    /* Use XPath to locate the water meter that has 
                     * the same meter number as the one in the Meter # text box.
                     * Store the water meter in an XmlNodeList variable. */
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + mtbMeterNumber.Text + "']")!;

                    /* If there is a water meter in the database with 
                     * the number that the user typed, locate that water meter 
                     * and display each of its values in the appropriate text box. */
                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        txtMake.Text = xnWaterMeter.NextSibling!.InnerText;
                        txtModel.Text = xnWaterMeter.NextSibling.NextSibling!.InnerText;
                        txtMeterSize.Text = xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText;
                    }
                }
            }
        }

        private void btnDeleteWaterMeter_Click(object sender, EventArgs e)
        {
            /* If the user clicks the Delete button, make sure that 
             * the right text box contains a meter number */
            if (string.IsNullOrEmpty(mtbMeterNumber.Text))
            {
                // If the user didn't provide a meter number, display a message box ...
                MessageBox.Show("You must type a water meter number if you want to delete one.",
                                "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
                // .. and stop the operation.
                return;
            }

            // Create an XML Dom object
            XmlDocument xdWaterMeters = new XmlDocument();
            /* Get the file that holds a list of water meters
             * and assign that file to a string variable. */
            string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";

            /* If the user provided a meter number and clicked the Find button,
             * check whether a file for water meters was previously created. */
            if (!File.Exists(strWaterMeters))
            {
                // If a file for water meters was not created already, display a message box...
                MessageBox.Show("There is no file for the water meters in the system.",
                                "Stellar Water Point",
                                MessageBoxButtons.OK, MessageBoxIcon.Information);
                // .. and stop the operation.
                return;
            }

            /* Since a file of water meters exists, open it.
             * Store the list of water meters in the XML Dom object that was previously created. */
            xdWaterMeters.Load(strWaterMeters);

            /* From the list of XML elements, get a list of elements based one named meter-number. */
            XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.GetElementsByTagName("meter-number");

            // Visit each XML node from the list
            foreach (XmlNode xnWaterMeter in xnlWaterMeters)
            {
                /* When you get to an element, check whether its meter number is 
                 * the same number the user had typed. */
                if (xnWaterMeter.InnerText == mtbMeterNumber.Text)
                {
                    /* If you find that meter number, enquire from 
                     * the user if the water meter must be deleted. 
                     * To get that information, display a message box with a Yes and a No buttons. */
                    if (MessageBox.Show("Are you sure you want to delete this water meter record from the system?",
                                    "Stellar Water Point",
                                    MessageBoxButtons.YesNo, MessageBoxIcon.Question) == DialogResult.Yes)
                    {
                        // If the user had clicked Yes, delete the water meter.
                        xdWaterMeters.DocumentElement.RemoveChild(xnWaterMeter.ParentNode!);
                        break;
                    }
                }
            }

            // Since the list of water meters has been changed, save its new version
            xdWaterMeters.Save(strWaterMeters);

            /* After the deletion operation, close the dialog box and
             * return to the Central form of water meters. */
            Close();
        }

        private void btnClose_Click(object sender, EventArgs e)
        {
            Close();
        }
    }
}

In the Solution Explorer, below the WaterMeters folder, double-click Central.cs
From the Toolbox, add two buttons to the form below the list view and on the right side of the Edit Water Meter button

Change the characteristics of the new buttons as follows:

Control	(Name)	Other Properties
ListView	lvwWaterMeters	FullRowSelect: True GridLines: True View: Details Anchor: Top, Bottom, Left, Right
Button	btnDeleteWateMeter	&Delete Water Meter... Anchor: Bottom, Right
Button	btnClose	&Close Anchor: Bottom, Right

In the Solution Explorer, below WaterMeters, double-click Central.cs to open its form
Double-click the Delete Water Meter button
Return to the Central form of the water meters and double-click the Close button

Change the document as follows:

using System.Xml;

namespace StellarWaterPoint10.WaterMeters
{
    public partial class Central : Form
    {
        public Central()
        {
            InitializeComponent();
        }

        private void ShowWaterMeters()
        {
            // Create an XML Dom reference
            XmlDocument xdWaterMeters = new XmlDocument();
            // Declare a string variable to have the file that holds a list of water meters
            string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";

            // Create a FileInfo object that holds a reference to the file of water meters
            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            // If you are about to display a list of water meters, first empty the list view
            lvwWaterMeters.Items.Clear();

            // Check whether a file for water meters was previously created.
            if (fiWaterMeters.Exists)
            {
                // If such a file exists, create a Stream for it
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    // Store the stream of water meters into the XML Dom that was created earlier
                    xdWaterMeters.Load(fsWaterMeters);
                    // Get a list of the water meter elements from the XML Dom object
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.ChildNodes;

                    int i = 1;

                    // Check each water meter
                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        // Create a list view item to hold a record of a water meter
                        ListViewItem lviWaterMeter = new ListViewItem(i.ToString());

                        lviWaterMeter.SubItems.Add(xnWaterMeter.FirstChild!.InnerText);
                        lviWaterMeter.SubItems.Add(xnWaterMeter.FirstChild.NextSibling!.InnerText);
                        lviWaterMeter.SubItems.Add(xnWaterMeter.FirstChild.NextSibling.NextSibling!.InnerText);
                        lviWaterMeter.SubItems.Add(xnWaterMeter.FirstChild.NextSibling.NextSibling.NextSibling!.InnerText);

                        // Pass the list view item to the list view object on the form
                        lvwWaterMeters.Items.Add(lviWaterMeter);

                        i++;
                    }
                }
            }
        }

        private void Central_Load(object sender, EventArgs e)
        {
            // When the open opens, make an attempt to display a list of water meters.
            ShowWaterMeters();
        }

        private void btnNewWaterMeter_Click(object sender, EventArgs e)
        {
            // Get a reference to the form used to add a water meter
            Create wm = new();
            // Create a FileInfo object
            FileInfo? fiWaterMeters = null;
            // Create a file stream object
            FileStream? fsWaterMeters = null;
            // Create an XML Dom object
            XmlDocument xdWaterMeters = new XmlDocument();
            // Declare a string for a file to hold a list of water meters
            string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";

            /* Display the form used to create a water meter. 
             * If the user finishes using that form and click the OK button... */
            if (wm.ShowDialog() == DialogResult.OK)
            {
                // Store the file of water meters into the FileInfo object that was previously created.
                fiWaterMeters = new FileInfo(strWaterMeters);

                /* Find out whether a list of water meters was previously created 
                 * and was stored in the string file declared above. */
                if (fiWaterMeters.Exists)
                {
                    /* If that file exists already, create a Stream object 
                     * for it with a read-only status. */
                    using (fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open,
                                                          FileAccess.Read, FileShare.Read))
                    {
                        // Pass the list of water meters to the XML Dom object created earlier
                        xdWaterMeters.Load(fsWaterMeters);
                    }
                }
                else
                {
                    // If a file for water meters was not previously created, create it now...
                    using (fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Create,
                                                          FileAccess.Write, FileShare.Write))
                    {
                        // and create the root XML element for it
                        xdWaterMeters.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                                              "<water-meters></water-meters>");
                        // Make sure you save the new file
                        xdWaterMeters.Save(fsWaterMeters);
                    }
                }

                // Now that the file exists, open it
                using (fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.OpenOrCreate,
                                                      FileAccess.ReadWrite, FileShare.ReadWrite))
                {
                    // Start creating a new Water Meter XML element
                    XmlElement xeWaterMeter = xdWaterMeters.CreateElement("water-meter");

                    /* Use the values that the user had typed in the Create form.
                     * Use those values to create the child elements of the new water meter node.
                     * Assign the combination of child elements to the new water meter node. */
                    xeWaterMeter.InnerXml = "<meter-number>" + wm.mtbMeterNumber.Text + "</meter-number>" +
                                            "<make>" + wm.txtMake.Text + "</make>" +
                                            "<model>" + wm.txtModel.Text + "</model>" +
                                            "<meter-size>" + wm.txtMeterSize.Text + "</meter-size>";
                    // Once the XML element is ready, add/append it to the XML Dom that was previously created.
                    xdWaterMeters.DocumentElement!.AppendChild(xeWaterMeter);
                    // Once the new element has been created and add it to the file, save that file
                    xdWaterMeters.Save(fsWaterMeters);
                }
            }

            /* Whenever the user has finished using the Create form, 
             * make an attempt to display the list of water meters. */
            ShowWaterMeters();
        }

        private void btnViewWaterMeter_Click(object sender, EventArgs e)
        {
            /* Get a reference to the dialog box that is used 
             * to view information about a water meter. */
            Details view = new();
            // Display that dialog box
            view.ShowDialog();

            // After using the dialog box, make an attempt to display the list of water meters.
            ShowWaterMeters();
        }

        private void btnEditWaterMeter_Click(object sender, EventArgs e)
        {
            /* Get a reference to the dialog box that is used 
             * to update the details of a water meter. */
            Editor editor = new();
            // Display that dialog box
            editor.ShowDialog();

            // After using the dialog box, make an attempt to display the list of water meters.
            ShowWaterMeters();
        }

        private void btnDeleteWateMeter_Click(object sender, EventArgs e)
        {
            Delete del = new Delete();
            del.ShowDialog();

            ShowWaterMeters();
        }

        private void btnClose_Click(object sender, EventArgs e)
        {
            Close();
        }
    }
}

To execute the application, on the main menu, click Debug -> Start Without Debugging:
On the Central form, click the Water Meters button:
On the Central form of the water meters, click the Delete Water Meter button:
In the Meter # text, type 588-279-663
Click the Find button:
Click the Delete button:
Read the text on the message box:
On the message box, click Yes
Close the forms and return to your programming environment
From the Windows Explorer, open the WaterMeters.xml file
Replace the content of the file with the provided file
Save the file
Return to your programming environment

Customers

Introduction

Obviously, customers are the ones who use the services of the bussiness whose application we are building. Obviously, a customer is represented by a business account, and a water meter must be associated to a customer's account. As seen with water meterrs, the application will use forms to create and manage customers accounts.

Customers Accounts

Our application will wuse a database that contains a list of customers. As seen with water meter records, we assume that some time to time, a user will want to view those records. To display a list of customers, we will create a form equipped with a list view.

Practical Learning: Displaying Customers Accounts

To create a folder, in the Solution Explorer, right-click the StellarWaterPoint1 project -> Add -> New Folder
Type Customers as the name of the folder
To create a form, in the Solution Explorer, right-click Customers -> Add -> Form (Windows Forms)...
Type Central
Click Add
In the Toolbox, click the ListView button and click the form

In the Properties window, change the characteristics of the list view as follows:

Control		(Name)	Other Properties
ListView		lvwCustomers	FullRowSelect: True GridLines: True View: Details Anchor: Top, Bottom, Left, Right

On the form, right-click the list view and click Edit Columns...

Create the columns as follows:

(Name)	Text	TextAlign	Width
colCustomerId	Id		40
colAccountNumber	Account #	Center	150
colAccountName	Account Name		200
colMeterNumber	Meter #	Center	100
colAccountType	Account Type		200
colAddress	Address		250
colCity	City		125
colCounty	County		125
colState	State	Center
colZIPCode	ZIP-Code	Center	125

Click OK
Doubte-click an unoccupied area of the form to generate its Load event

Change the document as follows:

using System.Xml;

namespace StellarWaterPoint3.Customers
{
    public partial class Central : Form
    {
        public Central()
        {
            InitializeComponent();
        }

        private void ShowCustomers()
        {
            int i = 1;

            lvwCustomers.Items.Clear();

            XmlDocument xdCustomers = new XmlDocument();
            string? strCustomers = @"C:\Stellar Water Point\Customers.xml";

            FileInfo? fiCustomers = new FileInfo(strCustomers);

            if (fiCustomers.Exists)
            {
                using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdCustomers.Load(fsCustomers);
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.ChildNodes;

                    foreach (XmlNode xnCustomer in xnlCustomers)
                    {
                        ListViewItem lviCustomer = new ListViewItem(i.ToString());

                        lviCustomer.SubItems.Add(xnCustomer.FirstChild!.InnerText);   // Account #
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling!.InnerText);   // Account Name
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling!.InnerText); // Meter #
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling!.InnerText);   // Account Type
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText);   // Address
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText);   // City
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText);   // County
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText);   // State
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText); // ZIP-Code

                        lvwCustomers.Items.Add(lviCustomer);

                        i++;
                    }
                }
            }
        }

        private void Central_Load(object sender, EventArgs e)
        {
            ShowCustomers();
        }       
    }
}

In the Solution Explorer, double-click WaterDistribution.cs to diaply the primary form of the application
From the Toolbox, add a button to the form

From the Properties window, change the characteristics of the button as follows:

Control		(Name)	Text	Font
Button		btnCustomers	&Customers...	Times New Roman, 24pt, style=Bold

On the form, double-click the Customers button

Implement the event as follows:

namespace StellarWaterPoint3
{
    public partial class WaterDistribution : Form
    {
        public WaterDistribution()
        {
            InitializeComponent();
        }

        private void WaterDistribution_Load(object sender, EventArgs e)
        {
            // If the directory for the database doesn't yet exist, create it
            Directory.CreateDirectory(@"C:\Stellar Water Point");
        }

        private void btnCustomers_Click(object sender, EventArgs e)
        {
            Customers.Central central = new Customers.Central();

            central.ShowDialog();
        }

        private void btnWaterMeters_Click(object sender, EventArgs e)
        {
            WaterMeters.Central central = new WaterMeters.Central();

            central.ShowDialog();
        }
    }
}

A Customer's Account

As mentioned already, our application will use a database that contains a list of customers. This means that a customer must have an account. We will create a form to let the user create an account. One important detail is that a customer must have a water meter. Therefore, each customer account must have an associated water meter. To set this up, on the form used to create a customer's account, we will add a text box that allows a user to specify and validate a water meter.

Practical Learning: Creating a Customer Account

In the Solution Explorer, right-click the Customers folder -> Add -> Form (Windows Forms)...
Type Create as the name of the file
Click Add

Design the form as follows:

Stellar Water Point - New Customer Account

Control	(Name)	Text	Other Properties
Label		&Account #:
MaskedTextBox	mtbAccountNumber		Masked: 0000-000-0000
Label		&Account Name:
TextBox	txtAccountName
Label		&Meter #:
MaskedTextBox	mtbMeterNumber		Masked: 000-000-000
Button	btnFindWaterMeter	&Find Water Meter
Label		Meter &Details:
TextBox	txtMeterDetails		Enabled: False
Label		&Account Type:
ComboBox	cbxAccountsTypes		Items: OTH - Other BUS - General Business RES - Residential Household SGO - Social/Government/Non - Profit Organization UUO - Unidentified or Unclassified Type of Organization WAT - Water Intensive Business(Laudromat, Hair Salon, Restaurant, etc
Label		&Address:
TextBox	txtAddress
Label		C&ity:
TextBox	txtCity
Label		C&ounty:
TextBox	txtCounty
Label		&State:
TextBox	txtState
Label		&ZIP-Code:
MaskedTextBox	mtbZIPCode		Masked: Zip-Code
Button	btnSaveCustomerAccount	S&ave Customer Account	DialogResult: OK
Button	btnClose	&Close	DialogResult: Cancel

Using the Properties window, change some characteristics of the form as follows:

FormBorderStyle: FixedDialog
Text:            Stellar Water Point - Customer Account Setup
StartPosition:   CenterScreen
AcceptButton:    btnSaveCustomerAccount
CancelButton:    btnClose
MinimizeBox:     False
MaximizeBox:     False

On the form, double-click the Find Water Meter button

Change the document as follows:

using System.Xml;

namespace StellarWaterPoint1.Customers
{
    public partial class Create : Form
    {
        public Create()
        {
            InitializeComponent();
        }

        private void btnFindWaterMeter_Click(object sender, EventArgs e)
        {
            // Create an XML Dom object
            XmlDocument xdWaterMeters = new XmlDocument();
            // Declare a string variable and assign the file of water meters to it
            string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
            // Create a FileInfo object to manage the file that has the water meters
            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            // Find out whether a file for water meters exists already
            if (fiWaterMeters.Exists)
            {
                // If a file for water meters exists already, create a Stream object for it
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open,
                                                                  FileAccess.Read, FileShare.Read))
                {
                    /* From the file of water meters, store the list of water meters 
                     * in the XML Dom that was previously created. */
                    xdWaterMeters.Load(fsWaterMeters);

                    /* Check the list of water meters. 
                     * Find a water meter that has the same name as the meter number that the user typed. */
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + mtbMeterNumber.Text + "']")!;

                    // If such a water meter exists...
                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        // ... store its details in the meter details text box.
                        txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                    }
                }
            }
        }
    }
}

In the Solution Explorer, below the Customers folder, double-click Central.cs
From the Toolbox, add a button to the form below the list view

Change the characteristics of the button as follows:

Control	(Name)	Other Properties
ListView	lvwCustomers
Button	btnCreateCustomerAccount	&Create Customer Account... Anchor: Bottom, Right

Double-click the Create Customer Account button

Change the document as follows:

using System.Xml;

namespace StellarWaterPoint3.Customers
{
    public partial class Central : Form
    {
        public Central()
        {
            InitializeComponent();
        }

        private void ShowCustomers()
        {
            int i = 1;

            lvwCustomers.Items.Clear();

            XmlDocument xdCustomers = new XmlDocument();
            string? strCustomers = @"C:\Stellar Water Point\Customers.xml";

            FileInfo? fiCustomers = new FileInfo(strCustomers);

            if (fiCustomers.Exists)
            {
                using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdCustomers.Load(fsCustomers);
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.ChildNodes;

                    foreach (XmlNode xnCustomer in xnlCustomers)
                    {
                        ListViewItem lviCustomer = new ListViewItem(i.ToString());

                        lviCustomer.SubItems.Add(xnCustomer.FirstChild!.InnerText);   // Account #
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling!.InnerText);   // Account Name
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling!.InnerText); // Meter #
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling!.InnerText);   // Account Type
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText);   // Address
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText);   // City
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText);   // County
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText);   // State
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText); // ZIP-Code

                        lvwCustomers.Items.Add(lviCustomer);

                        i++;
                    }
                }
            }
        }

        private void Central_Load(object sender, EventArgs e)
        {
            // When the form opens, try displaying the list of customers
            ShowCustomers();
        }

        private void btnCreateCustomerAccount_Click(object sender, EventArgs e)
        {
            Create create = new Create();

            if (create.ShowDialog() == DialogResult.OK)
            {
                /* Make sure the user provides an account number for the new account. 
                 * If not, don't create the account. */
                if (string.IsNullOrEmpty(create.mtbAccountNumber.Text))
                {
                    MessageBox.Show("You must provide an account number for the new customer. " +
                                    "Otherwise, the account cannot be created.",
                                    "Stellar Water Point",
                                    MessageBoxButtons.OK, MessageBoxIcon.Information);

                    return;
                }

                /* If the meter details text box is empty, it means the user didn't enter
                 * a meter number, in which case there is no water meter associated 
                 * with the account. The account cannot be created. */
                if (string.IsNullOrEmpty(create.txtMeterDetails.Text))
                {
                    MessageBox.Show("You must enter a water meter to associate with a new customer's account.",
                                    "Stellar Water Point",
                                    MessageBoxButtons.OK, MessageBoxIcon.Information);
                    
                    return;
                }
                
                // Create a FileInfo object that will be used to manage a file
                FileInfo? fiCustomers = null;
                // Start a Stream object that will be used to manage a file
                FileStream? fsCustomers = null;
                // Create an XML Dom
                XmlDocument xdCustomers = new XmlDocument();
                // Declare a string variable for the file that contains a list of customers
                string? strCustomers = @"C:\Stellar Water Point\Customers.xml";
                
                // Pass the file of customers to the FileInfo object that was started
                fiCustomers = new FileInfo(strCustomers);

                // Find out whether that file was already created
                if (fiCustomers.Exists)
                {
                    /* If that file was already created, open it through 
                     * the Stream object that was previously initiated. */
                    using (fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open,
                                                        FileAccess.Read, FileShare.Read))
                    {
                        // Pass the Stream object to the XML Dom that was previously created.
                        xdCustomers.Load(fsCustomers);
                    }
                }
                else
                {
                    /* If the file of customers was not created already, start by 
                     * initializing the Stream object that was previously initiated. */
                    using (fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Create, FileAccess.Write, FileShare.Write))
                    {
                        // Create a root to start the XML file
                        xdCustomers.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                                            "<customers></customers>");
                        // Once the file has been started, save it
                        xdCustomers.Save(fsCustomers);
                    }
                }

                // Now that we have an XML file for customers, open it
                using (fsCustomers = new FileStream(fiCustomers.FullName, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite))
                {
                    /* We want to create an XML element to be added to the XML file.
                     * To start, create an XML element named "customer". */
                    XmlElement xeCustomer = xdCustomers.CreateElement("customer");

                    // Create/Format the child nodes of the "customer" element
                    xeCustomer.InnerXml = "<account-number>" + create.mtbAccountNumber.Text + "</account-number>" +
                                          "<account-name>"   + create.txtAccountName.Text   + "</account-name>"   +
                                          "<meter-number>"   + create.mtbMeterNumber.Text   + "</meter-number>"   +
                                          "<account-type>"   + create.cbxAccountsTypes.Text + "</account-type>"   +
                                          "<address>"        + create.txtAddress.Text       + "</address>"        +
                                          "<city>"           + create.txtCity.Text          + "</city>"           +
                                          "<county>"         + create.txtCounty.Text        + "</county>"         +
                                          "<state>"          + create.txtState.Text         + "</state>"          +
                                          "<zip-code>"       + create.mtbZIPCode.Text       + "</zip-code>";
                    xdCustomers.DocumentElement!.AppendChild(xeCustomer);
                    xdCustomers.Save(fsCustomers);
                }
            }

            ShowCustomers();
        }
    }
}

To execute the application, on the main menu, click Debug -> Start Without Debugging:
On the Water Distribution form, click the Customers button:
On the Central form of the customers, click the Create Customer Account button:
In the account # text box, type 9279-570-8394
In the meter # text box, type 799-528-461
Click the Find water meter button

Enter the other values as follows:

Account #:    9279-570-8394
Account Name: Thomas Stones
Meter #:      799-528-461
Account Type: RES - Residential Household
Address:      10252 Broward Ave #D4
City:         Frederick
County:       Frederick
State:        MD
ZIP-Code:     21703-4422

Click Save Customer Account

In the same way, create the following two records:

Account #	Account Name	Meter #	Account Type	Address	City	County	State	ZIP-Code
4086-938-4783	Hernola Dough	594-827-359	UUO - Unidentified or Unclassified Type of Organization	10 10 Hexagonal Drv	Winston	Yoke	Penn	11402-4411
7080-583-5947	Sunny Yard	827-508-248	WAT - Water Intensive Business(Laudromat, Hair Salon, Restaurant, etc	663 Sherry Wood East Street	Shimpstown	Franklin	PA	17236-2626

Close the forms and return to your programming environment

A Review of a Customer's Account

Practical Learning: Creating a Water Meter Record

To create a form, in the Solution Explorer, right-click Customers -> Add -> Form (Windows Forms)...
For the Name of the form, type Details
Press Enter

Design the form as follows:

Stellar Water Point - New Customer Account

Control	(Name)	Text	Other Properties
Label		&Account #:
MaskedTextBox	mtbAccountNumber		Masked: 0000-000-0000
Button	btnFindCustomerAccount	&Find Customer Account
Label		Account Name:
TextBox	txtAccountName		Enabled: False
Label		Meter #:
TextBox	txtMeterNumber		Enabled: False
Label		Meter Details:
TextBox	txtMeterDetails		Enabled: False
Label		Account Type:
TextBox	txtAccountType		Enabled: False
Label		Address:
TextBox	txtAddress		Enabled: False
Label		City:
TextBox	txtCity		Enabled: False
Label		County:
TextBox	txtCounty		Enabled: False
Label		State:
TextBox	txtState		Enabled: False
Label		ZIP-Code:	Enabled: False
TextBox	txtZIPCode		Enabled: False
Button	btnClose	&Close

Using the Properties window, change some characteristics of the form as follows:

FormBorderStyle: FixedDialog
Text:            Stellar Water Point - Customer Account Setup
StartPosition:   CenterScreen
MinimizeBox:     False
MaximizeBox:     False

On the form, double-click the Find Cust&omer Account button

Implement the event as follows:

using System.Xml;

namespace StellarWaterPoint3.Customers
{
    public partial class Details : Form
    {
        public Details()
        {
            InitializeComponent();
        }

        private void btnFindCustomerAccount_Click(object sender, EventArgs e)
        {
            XmlDocument xdCustomers = new XmlDocument();
            string? strCustomers = @"C:\Stellar Water Point\Customers.xml";

            FileInfo? fiCustomers = new FileInfo(strCustomers);

            string strMeterNumber = string.Empty;

            if (fiCustomers.Exists)
            {
                using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdCustomers.Load(fsCustomers);
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + mtbAccountNumber.Text + "']")!;

                    foreach (XmlNode xnCustomer in xnlCustomers)
                    {
                        //mtbAccountNumber.Text = xnCustomer.NextSibling!.InnerText;   // Meter #
                        txtAccountName.Text   = xnCustomer.NextSibling!.InnerText; // Account Name
                        txtMeterNumber.Text   = xnCustomer.NextSibling.NextSibling!.InnerText;   // Meter Number
                        strMeterNumber        = xnCustomer.NextSibling.NextSibling!.InnerText;   // Meter Number
                        txtAccountType.Text   = xnCustomer.NextSibling.NextSibling.NextSibling!.InnerText;   // Account Type
                        txtAddress.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // Address
                        txtCity.Text          = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // City
                        txtCounty.Text        = xnCustomer.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;   // County
                        txtState.Text         = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;   // State
                        txtZIPCode.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText; // ZIP-Code
                    }
                }
            }

            XmlDocument xdWaterMeters = new XmlDocument();
            string? strWaterMeters = @"C:\Stellar Water Point6\WaterMeters.xml";

            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            if (fiWaterMeters.Exists)
            {
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterMeters.Load(fsWaterMeters);
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                    }
                }
            }
        }
    }
}

Return to the form and double-click the Close button

Implement the event as follows:

using System.Xml;

namespace StellarWaterPoint3.Customers
{
    public partial class Details : Form
    {
        public Details()
        {
            InitializeComponent();
        }

        private void btnFindCustomerAccount_Click(object sender, EventArgs e)
        {
            // Create an XML DOM object for the customers records
            XmlDocument xdCustomers = new XmlDocument();
            // Declare a variable for a file that holds the list of customers
            string? strCustomers = @"C:\Stellar Water Point6\Customers.xml";

            // Create a FileInfo object for the customers
            FileInfo? fiCustomers = new FileInfo(strCustomers);

            // We will need to know the water meter associated with this customer account
            string strMeterNumber = string.Empty;

            // Check whether the file that holds a list of customers exists
            if (fiCustomers.Exists)
            {
                // If that exists, open it and pass it to a FileStream object
                using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    // Get the list of customers and pass the records to the XML DOM object created earlier
                    xdCustomers.Load(fsCustomers);
                    // Create an XmlNodeList list of customers using XPath
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + mtbAccountNumber.Text + "']")!;

                    // Check each node of the XML record and display its values in each Windows control on the form
                    foreach (XmlNode xnCustomer in xnlCustomers)
                    {
                        //mtbAccountNumber.Text = xnCustomer.NextSibling!.InnerText;   // Meter #
                        txtAccountName.Text = xnCustomer.NextSibling!.InnerText; // Account Name
                        txtMeterNumber.Text = xnCustomer.NextSibling.NextSibling!.InnerText;   // Meter Number
                        strMeterNumber = xnCustomer.NextSibling.NextSibling!.InnerText;   // Meter Number
                        txtAccountType.Text = xnCustomer.NextSibling.NextSibling.NextSibling!.InnerText;   // Account Type
                        txtAddress.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // Address
                        txtCity.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // City
                        txtCounty.Text = xnCustomer.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;   // County
                        txtState.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;   // State
                        txtZIPCode.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText; // ZIP-Code
                    }
                }
            }

            // Create an XML DOM object for the water meters records
            XmlDocument xdWaterMeters = new XmlDocument();
            // Declare a variable for a file that holds the list of water meters
            string? strWaterMeters = @"C:\Stellar Water Point6\WaterMeters.xml";

            // Create a FileInfo object for the customers
            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            // Check whether the file that holds a list of water meters exists
            if (fiWaterMeters.Exists)
            {
                // Get the list of water meters and pass the records to the XML DOM object
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    // Get the list of water meters and pass the records to the XML DOM object
                    xdWaterMeters.Load(fsWaterMeters);
                    // Create an XmlNodeList list of water meters using XPath
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    // Check each node of the XML record
                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        /* Get the values for the water meter.
                         * Create a sentence and display it in the Meter Details text box. */
                        txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                    }
                }
            }
        }

        private void btnClose_Click(object sender, EventArgs e)
        {
            Close();
        }
    }
}

In the Solution Explorer, below the Customers folder, double-click Central.cs to open its form
From the Toolbox, add a button to the form below the list view and to the right of the Create Customer Account button

Change the characteristics of the button as follows:

Control		(Name)	Other Properties
Button		btnViewCustomerAccount	&View Customer Account... Anchor: Bottom, Right

Double-click the View Customer Account button

Change the document as follows:

using System.Xml;

namespace StellarWaterPoint3.Customers
{
    public partial class Details : Form
    {
        public Details()
        {
            InitializeComponent();
        }

        private void btnFindCustomerAccount_Click(object sender, EventArgs e)
        {
            XmlDocument xdCustomers = new XmlDocument();
            string? strCustomers = @"C:\Stellar Water Point6\Customers.xml";

            FileInfo? fiCustomers = new FileInfo(strCustomers);

            string strMeterNumber = string.Empty;

            if (fiCustomers.Exists)
            {
                using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdCustomers.Load(fsCustomers);
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + mtbAccountNumber.Text + "']")!;

                    foreach (XmlNode xnCustomer in xnlCustomers)
                    {
                        //mtbAccountNumber.Text = xnCustomer.NextSibling!.InnerText; // Meter #
                        txtAccountName.Text     = xnCustomer.NextSibling!.InnerText; // Account Name
                        txtMeterNumber.Text     = xnCustomer.NextSibling.NextSibling!.InnerText;   // Meter Number
                        strMeterNumber          = xnCustomer.NextSibling.NextSibling!.InnerText;   // Meter Number
                        txtAccountType.Text     = xnCustomer.NextSibling.NextSibling.NextSibling!.InnerText;   // Account Type
                        txtAddress.Text         = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // Address
                        txtCity.Text            = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // City
                        txtCounty.Text          = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;   // County
                        txtState.Text           = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;   // State
                        txtZIPCode.Text         = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText; // ZIP-Code
                    }
                }
            }

            XmlDocument xdWaterMeters = new XmlDocument();
            string? strWaterMeters = @"C:\Stellar Water Point6\WaterMeters.xml";

            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            if (fiWaterMeters.Exists)
            {
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterMeters.Load(fsWaterMeters);
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                    }
                }
            }
        }
    }
}

To execute the application, on the main menu, click Debug -> Start Without Debugging
On the Water Distribution form, click the Customers button:
On the Central form of customers, click the View Customer Account button:
In the Account # text box, type 4086-938-4783
Click the Find Customer Account button:
Close the Details form
Close the forms and return to your programming environment

Updating a Customer's Account

Practical Learning: Updating a Water Meter

To create a form, in the Solution Explorer, right-click WaterMeters -> Add -> Form (Windows Forms)...
For the Name of the file, type Editor as the name of the form
Click Add
Resize the Editor form to have the same size as the Create form of the Customers section
Copy everything from the Create form of the Customers section and paste it in the Editor form of the Customers section

Change the design of the form as follows:

Stellar Water Point - New Customer Account

Control	(Name)	Text	Other Properties
Button	btnFindCustomerAccount	&Find Customer Account
Button	btnUpdateWateMeter	&Update Water Meter	DialogResult: OK
Button	btnClose	&Close	DialogResult: Cancel

Using the Properties window, change some characteristics of the form as follows:

FormBorderStyle: FixedDialog
Text:            Stellar Water Point - Customer Account Editor
StartPosition:   CenterScreen
AcceptButton:    btnUpdateWateMeter
CancelButton:    btnClose
MinimizeBox:     False
MaximizeBox:     False

On the form, double-click the Find Customer Account button

Change the document as follows:

using System.Xml;

namespace StellarWaterPoint3.Customers
{
    public partial class Editor : Form
    {
        public Editor()
        {
            InitializeComponent();
        }

        private void btnFindCustomerAccount_Click(object sender, EventArgs e)
        {
            XmlDocument xdCustomers = new XmlDocument();
            string? strCustomers = @"C:\Stellar Water Point6\Customers.xml";

            FileInfo? fiCustomers = new FileInfo(strCustomers);

            string strMeterNumber = string.Empty;

            if (fiCustomers.Exists)
            {
                using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdCustomers.Load(fsCustomers);
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + mtbAccountNumber.Text + "']")!;

                    foreach (XmlNode xnCustomer in xnlCustomers)
                    {
                        //mtbAccountNumber.Text = xnCustomer.NextSibling!.InnerText;   // Meter #
                        txtAccountName.Text   = xnCustomer.NextSibling!.InnerText; // Account Name
                        mtbMeterNumber.Text   = xnCustomer.NextSibling.NextSibling!.InnerText;   // Meter Number
                        strMeterNumber        = xnCustomer.NextSibling.NextSibling!.InnerText;   // Meter Number
                        cbxAccountsTypes.Text = xnCustomer.NextSibling.NextSibling.NextSibling!.InnerText;   // Account Type
                        txtAddress.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // Address
                        txtCity.Text          = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // City
                        txtCounty.Text        = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;   // County
                        txtState.Text         = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;   // State
                        mtbZIPCode.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText; // ZIP-Code
                    }
                }
            }

            XmlDocument xdWaterMeters = new XmlDocument();
            string? strWaterMeters = @"C:\Stellar Water Point6\WaterMeters.xml";

            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            if (fiWaterMeters.Exists)
            {
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterMeters.Load(fsWaterMeters);
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                    }
                }
            }
        }
    }
}

Return to the form and double-click the Find Water Meter button

Implement the event as follows:

using System.Xml;

namespace StellarWaterPoint3.Customers
{
    public partial class Editor : Form
    {
        public Editor()
        {
            InitializeComponent();
        }

        private void btnFindCustomerAccount_Click(object sender, EventArgs e)
        {
            XmlDocument xdCustomers = new XmlDocument();
            string? strCustomers = @"C:\Stellar Water Point6\Customers.xml";

            FileInfo? fiCustomers = new FileInfo(strCustomers);

            string strMeterNumber = string.Empty;

            if (fiCustomers.Exists)
            {
                using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdCustomers.Load(fsCustomers);
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + mtbAccountNumber.Text + "']")!;

                    foreach (XmlNode xnCustomer in xnlCustomers)
                    {
                        //mtbAccountNumber.Text = xnCustomer.NextSibling!.InnerText;
                        txtAccountName.Text   = xnCustomer.NextSibling!.InnerText;
                        mtbMeterNumber.Text   = xnCustomer.NextSibling.NextSibling!.InnerText;
                        strMeterNumber        = xnCustomer.NextSibling.NextSibling!.InnerText;
                        cbxAccountsTypes.Text = xnCustomer.NextSibling.NextSibling.NextSibling!.InnerText;
                        txtAddress.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;
                        txtCity.Text          = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;
                        txtCounty.Text        = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtState.Text         = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        mtbZIPCode.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                    }
                }
            }

            XmlDocument xdWaterMeters = new XmlDocument();
            string? strWaterMeters = @"C:\Stellar Water Point6\WaterMeters.xml";

            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            if (fiWaterMeters.Exists)
            {
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterMeters.Load(fsWaterMeters);
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                    }
                }
            }
        }

        private void btnFindWateMeter_Click(object sender, EventArgs e)
        {
            XmlDocument xdWaterMeters = new XmlDocument();
            string? strWaterMeters = @"C:\Stellar Water Point6\WaterMeters.xml";
            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            if (fiWaterMeters.Exists)
            {
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open,
                                                                  FileAccess.Read, FileShare.Read))
                {
                    xdWaterMeters.Load(fsWaterMeters);

                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + mtbMeterNumber.Text + "']")!;

                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                    }
                }
            }
        }
    }
}

In the Solution Explorer, below the Customers folder, double-click Central.cs
From the Toolbox, add a button to the form below the list view and on the right side of the View Customer Account button

Change the characteristics of the button as follows:

Control	(Name)	Text	Other Properties
ListView	lvwCustomers		No Change
Button	btnNewCustomerAccount		No Change
Button	btnViewCustomerAccount		No Change
Button	btnEditCustomerAccount	&Edit Water Meter...	Anchor: Bottom, Right

Display the Central form of the Customers folder
Double-click the Update Water Meter button

Implement the event as follows:

using System.Xml;

namespace StellarWaterPoint3.Customers
{
    public partial class Central : Form
    {
        public Central()
        {
            InitializeComponent();
        }

        private void ShowCustomers()
        {
            . . .
        }

        private void Central_Load(object sender, EventArgs e)
        {
            ShowCustomers();
        }

        private void btnCreateCustomerAccount_Click(object sender, EventArgs e)
        {
            . . .
        }

        private void ViewCustomerAccount_Click(object sender, EventArgs e)
        {
            Details det = new Details();

            det.ShowDialog();
        }

        private void btnEditCustomerAccount_Click(object sender, EventArgs e)
        {
            Editor editor = new();
            XmlDocument xdCustomers = new XmlDocument();
            string? strCustomers = @"C:\Stellar Water Point6\Customers.xml";

            if (editor.ShowDialog() == DialogResult.OK)
            {
                xdCustomers.Load(strCustomers);

                XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.GetElementsByTagName("account-number");

                foreach (XmlNode xnCustomer in xnlCustomers)
                {
                    if (xnCustomer.InnerText.Contains(editor.mtbAccountNumber.Text))
                    {
                        xnCustomer.ParentNode!.InnerXml = "<account-number>" + editor.mtbAccountNumber.Text + "</account-number>" +
                                              "<account-name>" + editor.txtAccountName.Text + "</account-name>" +
                                              "<meter-number>" + editor.mtbMeterNumber.Text + "</meter-number>" +
                                              "<account-type>" + editor.cbxAccountsTypes.Text + "</account-type>" +
                                              "<address>" + editor.txtAddress.Text + "</address>" +
                                              "<city>" + editor.txtCity.Text + "</city>" +
                                              "<county>" + editor.txtCounty.Text + "</county>" +
                                              "<state>" + editor.txtState.Text + "</state>" +
                                              "<zip-code>" + editor.mtbZIPCode.Text + "</zip-code>";

                        xdCustomers.Save(strCustomers);
                        break;
                    }
                }
            }

            ShowCustomers();    
        }
    }
}

To execute the application, on the main menu, click Debug -> Start Without Debugging
On the main form of the application, click the Customers button:
Click the Edit Customer Account button:
In the Account # text, type 4086-938-4783
Click the Find Customer Account button

Change the values as follows:

Account Name: Bernotte's Doughnuts
Meter #:      580-742-825 and click Find Water Meter
Account Type: BUS	- General Business
Address:      10103 Hexagon Drive
City:         Winterstown
County:       York
State:        PA
ZIP-Code:     17402-8828

Stellar Water Point - New Water Meter

Click the Update Customer Account button:
Close the forms and return to your programming environment

Deleting a Customer's Account

If a record is not necessary anymore on a database, the user may want to remove it. To assist the user with this operation, we will create a form withe necessary buttons.

Practical Learning: Deleting a Customer Account

To create a form, in the Solution Explorer, right-click WaterMeters -> Add -> Form(Windows Forms)...
In the Name text box, replace the string with Delete as the name of the form
Press Enter
Resize the Delete form to have the same size as the Details form
Copy everything from the Details form and paste it in the Delete form

Change the bottom button as follows:

Stellar Water Point - New Water Meter

Control	(Name)	Text	Othe Properties
Button	btnDeleteCustomerAccount	&Delete Water Meter	DialogResult: OK
Button	btnClose	&Close	DialogResult: Cancel

Using the Properties window, change some characteristics of the form as follows:

FormBorderStyle: FixedDialog
Text:            Stellar Water Point - Customer Account Deletion
StartPosition:   CenterScreen
AcceptButton:    btnDeleteCustomerAccount
CancelButton:    btnClose
MinimizeBox:     False
MaximizeBox:     False

On the form, double-click the Find Customer Account button

Change the document as tollows:

using System.Xml;

namespace StellarWaterPoint3.Customers
{
    public partial class Delete : Form
    {
        public Delete()
        {
            InitializeComponent();
        }

        private void btnFindCustomerAccount_Click(object sender, EventArgs e)
        {
            // Create an XML DOM object for the customers records
            XmlDocument xdCustomers = new XmlDocument();
            // Declare a variable for a file that holds the list of customers
            string? strCustomers = @"C:\Stellar Water Point6\Customers.xml";

            // Create a FileInfo object for the customers
            FileInfo? fiCustomers = new FileInfo(strCustomers);

            // We will need to know the water meter associated with this customer account
            string strMeterNumber = string.Empty;

            // Check whether the file that holds a list of customers exists
            if (fiCustomers.Exists)
            {
                // If that exists, open it and pass it to a FileStream object
                using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    // Get the list of customers and pass the records to the XML DOM object created earlier
                    xdCustomers.Load(fsCustomers);
                    // Create an XmlNodeList list of customers using XPath
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + mtbAccountNumber.Text + "']")!;

                    // Check each node of the XML record and display its values in each Windows control on the form
                    foreach (XmlNode xnCustomer in xnlCustomers)
                    {
                        //mtbAccountNumber.Text = xnCustomer.NextSibling!.InnerText;
                        txtAccountName.Text = xnCustomer.NextSibling!.InnerText;
                        txtMeterNumber.Text = xnCustomer.NextSibling.NextSibling!.InnerText;
                        strMeterNumber = xnCustomer.NextSibling.NextSibling!.InnerText;
                        txtAccountType.Text = xnCustomer.NextSibling.NextSibling.NextSibling!.InnerText;
                        txtAddress.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;
                        txtCity.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;
                        txtCounty.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtState.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtZIPCode.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                    }
                }
            }

            // Create an XML DOM object for the water meters records
            XmlDocument xdWaterMeters = new XmlDocument();
            // Declare a variable for a file that holds the list of water meters
            string? strWaterMeters = @"C:\Stellar Water Point6\WaterMeters.xml";

            // Create a FileInfo object for the customers
            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            // Check whether the file that holds a list of water meters exists
            if (fiWaterMeters.Exists)
            {
                // Get the list of water meters and pass the records to the XML DOM object
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    // Get the list of water meters and pass the records to the XML DOM object
                    xdWaterMeters.Load(fsWaterMeters);
                    // Create an XmlNodeList list of water meters using XPath
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    // Check each node of the XML record
                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        /* Get the values for the water meter.
                         * Create a sentence and display it in the Meter Details text box. */
                        txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                    }
                }
            }
        }
    }
}

In the Solution Explorer, below the Customers folder, double-click Central.cs
From the Toolbox, add two buttons to the form below the list view and on the right side of the Edit Customer Acount button

Change the characteristics of the new buttons as follows:

Control	(Name)	Other Properties
ListView	lvwCustomers
Button	btnDeleteCustomerAcount	&Delete Customer Acount... Anchor: Bottom, Right
Button	btnClose	&Close Anchor: Bottom, Right

Double-click the Delete Customer Account button
Return to the Central form of the water meters and double-click the Close button

Change the document as follows:

using System.Xml;

namespace StellarWaterPoint3.Customers
{
    public partial class Central : Form
    {
        public Central()
        {
            InitializeComponent();
        }

        private void ShowCustomers()
        {
            int i = 1;

            lvwCustomers.Items.Clear();

            XmlDocument xdCustomers = new XmlDocument();
            string? strCustomers = @"C:\Stellar Water Point6\Customers.xml";

            FileInfo? fiCustomers = new FileInfo(strCustomers);

            if (fiCustomers.Exists)
            {
                using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdCustomers.Load(fsCustomers);
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.ChildNodes;

                    foreach (XmlNode xnCustomer in xnlCustomers)
                    {
                        ListViewItem lviCustomer = new ListViewItem(i.ToString());

                        lviCustomer.SubItems.Add(xnCustomer.FirstChild!.InnerText);   // Account #
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling!.InnerText);   // Account Name
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling!.InnerText); // Meter #
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling!.InnerText);   // Account Type
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText);   // Address
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText);   // City
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText);   // County
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText);   // State
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText); // ZIP-Code

                        lvwCustomers.Items.Add(lviCustomer);

                        i++;
                    }
                }
            }
        }

        private void Central_Load(object sender, EventArgs e)
        {
            ShowCustomers();
        }

        private void btnCreateCustomerAccount_Click(object sender, EventArgs e)
        {
            Create create = new Create();

            if (create.ShowDialog() == DialogResult.OK)
            {
                /* Make sure the user provides an account number for the new account. 
                 * If not, don't create the account. */
                if (string.IsNullOrEmpty(create.mtbAccountNumber.Text))
                {
                    MessageBox.Show("You must provide an account number for the new customer. " +
                                    "Otherwise, the account cannot be created.",
                                    "Stellar Water Point",
                                    MessageBoxButtons.OK, MessageBoxIcon.Information);

                    return;
                }

                /* If the meter details text box is empty, it means the user didn't enter
                 * a meter number, in which case there is no water meter associated 
                 * with the account. The account cannot be created. */
                if (string.IsNullOrEmpty(create.txtMeterDetails.Text))
                {
                    MessageBox.Show("You must enter a water meter to associate with a new customer's account.",
                                    "Stellar Water Point",
                                    MessageBoxButtons.OK, MessageBoxIcon.Information);

                    return;
                }

                // Create a FileInfo object that will be used to manage a file
                FileInfo? fiCustomers = null;
                // Start a Stream object that will be used to manage a file
                FileStream? fsCustomers = null;
                // Create an XML Dom
                XmlDocument xdCustomers = new XmlDocument();
                // Declare a string variable for the file that contains a list of customers
                string? strCustomers = @"C:\Stellar Water Point6\Customers.xml";

                // Pass the file of customers to the FileInfo object that was started
                fiCustomers = new FileInfo(strCustomers);

                // Find out whether that file was already created
                if (fiCustomers.Exists)
                {
                    /* If that file was already created, open it through 
                     * the Stream object that was previously initiated. */
                    using (fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open,
                                                        FileAccess.Read, FileShare.Read))
                    {
                        // Pass the Stream object to the XML Dom that was previously created.
                        xdCustomers.Load(fsCustomers);
                    }
                }
                else
                {
                    /* If the file of customers was not created already, start by 
                     * initializing the Stream object that was previously initiated. */
                    using (fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Create, FileAccess.Write, FileShare.Write))
                    {
                        // Create a root to start the XML file
                        xdCustomers.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                                            "<customers></customers>");
                        // Once the file has been started, save it
                        xdCustomers.Save(fsCustomers);
                    }
                }

                // Now that we have an XML file for customers, open it
                using (fsCustomers = new FileStream(fiCustomers.FullName, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite))
                {
                    /* We want to create an XML element to be added to the XML file.
                     * To start, create an XML element named "customer". */
                    XmlElement xeCustomer = xdCustomers.CreateElement("customer");

                    // Create/Format the child nodes of the "customer" element
                    xeCustomer.InnerXml = "<account-number>" + create.mtbAccountNumber.Text + "</account-number>" +
                                          "<account-name>" + create.txtAccountName.Text + "</account-name>" +
                                          "<meter-number>" + create.mtbMeterNumber.Text + "</meter-number>" +
                                          "<account-type>" + create.cbxAccountsTypes.Text + "</account-type>" +
                                          "<address>" + create.txtAddress.Text + "</address>" +
                                          "<city>" + create.txtCity.Text + "</city>" +
                                          "<county>" + create.txtCounty.Text + "</county>" +
                                          "<state>" + create.txtState.Text + "</state>" +
                                          "<zip-code>" + create.mtbZIPCode.Text + "</zip-code>";
                    xdCustomers.DocumentElement!.AppendChild(xeCustomer);
                    xdCustomers.Save(fsCustomers);
                }
            }

            ShowCustomers();
        }

        private void ViewCustomerAccount_Click(object sender, EventArgs e)
        {
            Details det = new Details();

            det.ShowDialog();
        }

        private void btnEditWaterMeter_Click(object sender, EventArgs e)
        {
            // This is the form that will be used to update a customer record
            Editor editor = new();
            // Create an XML DOM object
            XmlDocument xdCustomers = new XmlDocument();
            // Prepare the path and name of the file that holds a list of customers 
            string? strCustomers = @"C:\Stellar Water Point6\Customers.xml";

            /* Display the Editor form.
             * Find out if the user clicked the Update Customer Account button when closing the Editor dialog box. */
            if (editor.ShowDialog() == DialogResult.OK)
            {
                // Get the customers records and store them in the above XML DOM object
                xdCustomers.Load(strCustomers);

                /* Create an XmlNodeList list that reprensents the XML elements from the list of customers.
                 * Call the XML DOM's GetElementsByTagName() method. 
                 * To use the account number elements as references, pass the name of the Account # element as argument. */
                XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.GetElementsByTagName("account-number");

                // Visit each XML element of the list of customers
                foreach (XmlNode xnCustomer in xnlCustomers)
                {
                    /* When you get to an element, find out if the value of it Account Number is 
                     * the same as the account number the user typed in the form. If that's the case, 
                     * change the value of each node of that element, using the values from the form. */
                    if (xnCustomer.InnerText.Contains(editor.mtbAccountNumber.Text))
                    {
                        xnCustomer.ParentNode!.InnerXml = "<account-number>" + editor.mtbAccountNumber.Text + "</account-number>" +
                                              "<account-name>" + editor.txtAccountName.Text + "</account-name>" +
                                              "<meter-number>" + editor.mtbMeterNumber.Text + "</meter-number>" +
                                              "<account-type>" + editor.cbxAccountsTypes.Text + "</account-type>" +
                                              "<address>" + editor.txtAddress.Text + "</address>" +
                                              "<city>" + editor.txtCity.Text + "</city>" +
                                              "<county>" + editor.txtCounty.Text + "</county>" +
                                              "<state>" + editor.txtState.Text + "</state>" +
                                              "<zip-code>" + editor.mtbZIPCode.Text + "</zip-code>";

                        // After updating the elements, save the updated file
                        xdCustomers.Save(strCustomers);
                        // After saving the file, stop searching
                        break;
                    }
                }
            }

            /* Now that the user has closed the Editor dialog box (and probably updated the XML file), 
             * redisplay the list of customers.*/
            ShowCustomers();
        }

        private void btnDeleteCustomerAcount_Click(object sender, EventArgs e)
        {
            // Here is the dialog box that the user will use to locate and delete a customer account
            Delete delete = new();
            // Create an XML DOM object
            XmlDocument xdCustomers = new XmlDocument();
            // Specify the file that holds a database of customers
            string? strCustomers = @"C:\Stellar Water Point6\Customers.xml";

            /* Open the Delete dialog box.
             * Find out if the user clicked the Delete Customer Account button to close the Delete dialog box. */
            if (delete.ShowDialog() == DialogResult.OK)
            {
                // If there is no file for the list of customers, don't do nothing
                if (!File.Exists(strCustomers))
                {
                    MessageBox.Show("There is no file for the customers accounts in the system.",
                                    "Stellar Water Point",
                                    MessageBoxButtons.OK, MessageBoxIcon.Information);
                    return;
                }
                // If the user didn't provide a valid account number, don't do nothing
                if (string.IsNullOrEmpty(delete.mtbAccountNumber.Text))
                {
                    MessageBox.Show("You must type an account number for the customer whose account you want to delete one.",
                                    "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
                    return;
                }

                // Open the file of customers records and put those records in our XML DOM object
                xdCustomers.Load(strCustomers);

                /* Create an XmlNodeList list of the customers records. 
                 * Use the Account Number node as reference. */
                XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.GetElementsByTagName("account-number");

                // Check each customer record as an XML element
                foreach (XmlNode xnCustomer in xnlCustomers)
                {
                    /* When you reach an element, find out whether its value is 
                     * the same as the account number the user typed on the form. */
                    if (xnCustomer.InnerText == delete.mtbAccountNumber.Text)
                    {
                        // If you find a matching record, find whether the user really wants to delete the record.
                        if (MessageBox.Show("Are you sure you want to remove this customer's account from the system?",
                                        "Stellar Water Point",
                                        MessageBoxButtons.YesNo, MessageBoxIcon.Question) == DialogResult.Yes)
                        {
                            // If the user really wants to delete the record, delete it...
                            xdCustomers.DocumentElement.RemoveChild(xnCustomer.ParentNode!);
                            // and stop searching
                            break;
                        }
                    }
                }

                // After removing the record, save the new version of the file 
                xdCustomers.Save(strCustomers);
            }

            /* Now that the user has closed the Delete dialog box (and probably deleted the XML file), 
             * redisplay the list of customers.*/
            ShowCustomers();
        }

        private void btnClose_Click(object sender, EventArgs e)
        {
            Close();
        }
    }
}

To execute the application, on the main menu, click Debug -> Start Without Debugging:
On the Central form, click the Customers button:
On the Central form of the customers, click the Delete Customer Account button:
In the Account # text box, type 7080-583-5947
Click the Find Customer Account button:
Click the Delete Customer Account button
Read the text on the message box.
On the message box, click Yes
Close the forms and return to your programming environment
From the Windows Explorer, open the Customers.xml file
Replace the content of the file with the provided file
Save the file
Return to your programming environment

Water Bills

Introduction

A water bill is a summary that indicates how much water a customer consumed and the value of that consumption. Our application will include a form to process a water bill. We will use another form that can be used to review an existing water bill. We will use another form to change or update a water bill that was previously processed. Finally, we will have a form that can be used to delete a water bill. In previous sections, we provided one Central form for the water meters and another Central form for the Customers. Those Central forms allow the user to navigate to the forms related to a section. Those sections included a form that provides a list of records. Because a water bill has too many values, we will not create a form that presents a list of water bills.

Practical Learning: Preparing Bills

In the Solution Explorer, right-click StellarWaterPoint1 -> Add -> New Folder
Type WaterBills as the name of the folder

A Water Bill

Our application will have a list of water meters. A record for each water meter must be created. To make this happen, we will equip the application with an appropriate form.

Practical Learning: Processing a Water Bill

To create a form, in the Solution Explorer, right-click WaterBills -> Add -> Form (Windows Forms)...
Type Create as the name of the file
Click Add

Design the form as follows:

Stellar Water Point - New Water Bill

Control	(Name)	Text	Other Properties
Label		Water Bill #:
TextBox	txtBillNumber
GroupBox		Customer Information
Label		Account #:
MaskedTextBox	mtbAccountNumber		Masked: 0000-000-0000
Button	btnFindCustomerAccount	Find Customer Account
Label		Customer Name:
TextBox	txtCustomerName
Label		Address:
TextBox	txtAddress
TextBox	txtCity
TextBox	txtCounty
TextBox	txtState
MaskedTextBox	mtbZIPCode		Masked: Zip-Code
Label		______________________________________________
Label		Meter Details:
TextBox	txtMeterDetails	Modifiers: Public
GroupBox		Meter Reading
Label		Meter Reading Start Date:
DateTimePicker	dtpMeterReadingStartDate
Label		Meter Reading End Date:
DateTimePicker	dtpMeterReadingEndDate
Label		Counter Reading Start:
TextBox	txtCounterReadingStart
Label		Counter Reading End:
TextBox	txtCounterReadingEnd
Button	btnEvaluateWaterBill	Evaluate Water Bill
GroupBox		Meter Result
Label		Billing Days:
TextBox	txtBillingDays		TextAlign: Right
Label		Total Gallons:
TextBox	txtTotalGallons		TextAlign: Right
Label		Total CCF:
TextBox	txtTotalCCF		TextAlign: Right
Label		First Tier Consumption:
TextBox	txtFirstTierConsumption		TextAlign: Right
Label		Second Tier:
TextBox	txtSecondTierConsumption		TextAlign: Right
Label		Last Tier:
TextBox	txtLastTierConsumption		TextAlign: Right
GroupBox		Consumption Charges
Label		Water Charges:
TextBox	txtWaterCharges		TextAlign: Right
Label		Sewer Charges:
TextBox	txtSewerCharges		TextAlign: Right
Label		Environment Charges:
TextBox	txtEnvironmentCharges		TextAlign: Right
Label		Total Charges:
TextBox	txtTotalCharges		TextAlign: Right
GroupBox		Taxes
Label		Local Taxes:
TextBox	txtLocalTaxes		TextAlign: Right
Label		State Taxes:
TextBox	txtStateTaxes		TextAlign: Right
GroupBox		Water Bill Payment
Label		Payment Due Date:
DateTimePicker	dtpPaymentDueDate
Label		Amount Due:
TextBox	txtAmountDue		TextAlign: Right
Label		Late Payment Due Date:
DateTimePicker	dtpLatePaymentDueDate
Label		Late Amount Due:
TextBox	txtLateAmountDue		TextAlign: Right
Button	btnSaveWaterBill	Save Water Bill
Button	btnClose	Close

On the form, double-click the Find Customer Account button

Change the document as follows:

using System.Xml;

namespace StellarWaterPoint3.WaterBills
{
    public partial class Create : Form
    {
        public Create()
        {
            InitializeComponent();
        }

        private void btnFindCustomerAccount_Click(object sender, EventArgs e)
        {
            XmlDocument xdCustomers = new XmlDocument();
            string? strCustomers    = @"C:\Stellar Water Point6\Customers.xml";

            FileInfo? fiCustomers   = new FileInfo(strCustomers);

            string strMeterNumber   = string.Empty;

            if (fiCustomers.Exists)
            {
                using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdCustomers.Load(fsCustomers);
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + mtbAccountNumber.Text + "']")!;

                    foreach (XmlNode xnCustomer in xnlCustomers)
                    {
                        txtAccountName.Text = xnCustomer.NextSibling!.InnerText;
                        strMeterNumber      = xnCustomer.NextSibling.NextSibling!.InnerText;
                        txtAccountType.Text = xnCustomer.NextSibling.NextSibling.NextSibling!.InnerText;
                        txtAddress.Text     = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;
                        txtCity.Text        = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;
                        txtCounty.Text      = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtState.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtZIPCode.Text     = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                    }
                }
            }

            XmlDocument xdWaterMeters = new XmlDocument();
            string? strWaterMeters = @"C:\Stellar Water Point6\WaterMeters.xml";

            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            if (fiWaterMeters.Exists)
            {
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterMeters.Load(fsWaterMeters);
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                    }
                }
            }
        }
    }
}

Return to the Water Bills - Create form and double-click the Meter Reading End Date date time picker

Implement the event as follows:

using System.Xml;

namespace StellarWaterPoint3.WaterBills
{
    public partial class Create : Form
    {
        public Create()
        {
            InitializeComponent();
        }

        private void btnFindCustomerAccount_Click(object sender, EventArgs e)
        {
            . . .
        }

        private void dtpMeterReadingEndDate_ValueChanged(object sender, EventArgs e)
        {
            TimeSpan tsDays = dtpMeterReadingEndDate.Value - dtpMeterReadingStartDate.Value;

            txtBillingDays.Text = (tsDays.Days + 1).ToString();
        }
    }
}

Return to the Water Bills - Create form and double-click the Evaluate Water Bill button

Implement the event as follows:

using System.Xml;

namespace StellarWaterPoint3.WaterBills
{
    public partial class Create : Form
    {
        public Create()
        {
            InitializeComponent();
        }

        private void btnFindCustomerAccount_Click(object sender, EventArgs e)
        {
            . . .
        }

        private void dtpMeterReadingEndDate_ValueChanged(object sender, EventArgs e)
        {
            . . .
        }

        (double a, double b, double c) CalculateTiers(string acnt, double total)
        {
            (double tier1, double tier2, double tier3) results = (0.00, 0.00, 0.00);

            switch (acnt)
            {
                case "RES":
                    results.tier1 = total * 41.50 / 10000.00;
                    results.tier2 = total * 32.50 / 10000.00;
                    results.tier3 = total * 26.00 / 10000.00;
                    break;
                case "SGO":
                    results.tier1 = total * 46 / 10000;
                    results.tier2 = total * 50 / 10000;
                    results.tier3 = total * 4 / 10000;
                    break;
                case "BUS":
                    results.tier1 = total * 45 / 10000;
                    results.tier2 = total * 30 / 10000;
                    results.tier3 = total * 25 / 10000;
                    break;
                case "UUO":
                    results.tier1 = total * 25 / 10000;
                    results.tier2 = total * 35 / 10000;
                    results.tier3 = total * 40 / 10000;
                    break;
                case "WAT":
                    results.tier1 = total * 50 / 10000;
                    results.tier2 = total * 40 / 10000;
                    results.tier3 = total * 10 / 10000;
                    break;
                default:
                    results.tier1 = total * (48.00 / 10000.00);
                    results.tier2 = total * (32.00 / 10000.00);
                    results.tier3 = total * (20.00 / 10000.00);
                    break;
            }

            return results;
        }

        private double CalculateSewerCharges(string acnt, double total)
        {
            double result;

            if (acnt == "RES")
            {
                result = total * 6.826941 / 100;
            }
            else if (acnt == "SGO")
            {
                result = total * 4.162522 / 100;
            }
            else if (acnt == "BUS")
            {
                result = total * 8.3136 / 100;
            }
            else if (acnt == "UUO")
            {
                result = total * 10.6247 / 100;
            }
            else if (acnt == "WAT")
            {
                result = total * 12.0535 / 100;
            }
            else // if (acnt == "OTH)"
            {
                result = total * 9.2065 / 100;
            }

            return result;
        }

        private double CalculateEnvironmentCharges(string acnt, double total)
        {
            double result;

            switch(acnt)
            {
                case "RES":
                    result = total * 0.022724;
                    break;
                case "SGO":
                    result = total * 0.118242;
                    break;
                case "BUS":
                    result = total * 0.161369;
                    break;
                case "UUO":
                    result = total * 0.082477;
                    break;
                case "WAT":
                    result = total * 0.413574;
                    break;
                default:
                    result = total * 0.221842;
                    break;
            }

            return result;
        }

        private double CalculateServiceCharges(string acnt, double total)
        {
            switch (acnt)
            {
                case "RES":
                    return total * 0.145748;
                case "SGO":
                    return total * 0.102246;
                case "BUS":
                    return total * 0.242627;
                case "UUO":
                    return total * 0.186692;
                case "WAT":
                    return total * 0.412628;
                default:
                    return total * 0.210248;
            }
        }

        private double CalculateLocalTaxes(string acnt, double total) => acnt switch
        {
            "RES" => total * 0.031574,
            "SGO" => total * 0.035026,
            "BUS" => total * 0.122517,
            "UUO" => total * 0.105737,
            "WAT" => total * 0.153248,
            _ => total * 0.125148
        };

        private double CalculateStateTaxes(string acnt, double total) => acnt switch
        {
            "RES" => total * 0.016724,
            "SGO" => total * 0.008779,
            "BUS" => total * 0.042448,
            "UUO" => total * 0.067958,
            "WAT" => total * 0.081622,
            _ => total * 0.013746
        };

        private DateTime SetPaymentDueDate(string acnt, DateTime date)
        {
            TimeSpan tsPaymentDueDate = new TimeSpan(1, 0, 0, 0);

            if (acnt == "RES")
            {
                tsPaymentDueDate = new TimeSpan(15, 0, 0, 0);
            }
            else if (acnt == "SGO")
            {
                tsPaymentDueDate = new TimeSpan(20, 0, 0, 0);
            }
            else if (acnt == "BUS")
            {
                tsPaymentDueDate = new TimeSpan(30, 0, 0, 0);
            }
            else if (acnt == "UUO")
            {
                tsPaymentDueDate = new TimeSpan(15, 0, 0, 0);
            }
            else if (acnt == "WAT")
            {
                tsPaymentDueDate = new TimeSpan(40, 0, 0, 0);
            }
            else
            {
                tsPaymentDueDate = new TimeSpan(35, 0, 0, 0);
            }

            return date + tsPaymentDueDate;
        }

        private DateTime SetLatePaymentDueDate(string acnt, DateTime date)
        {
            switch (acnt)
            {
                case "RES":
                    return date + new TimeSpan(30, 0, 0, 0);
                case "SGO":
                    return date + new TimeSpan(40, 0, 0, 0);
                case "BUS":
                    return date + new TimeSpan(50, 0, 0, 0);
                case "UUO":
                    return date + new TimeSpan(60, 0, 0, 0);
                case "WAT":
                    return date + new TimeSpan(65, 0, 0, 0);
                default:
                    return date + new TimeSpan(45, 0, 0, 0);
            }
        }

        private double CalculateLateAmountDue(string acnt, double amt) => acnt switch
        {
            "RES" => amt + 8.95,
            "SGO" => amt + (amt / 4.575),
            "BUS" => amt + (amt / 12.315),
            "UUO" => amt + (amt / 7.425),
            "WAT" => amt + (amt / 15.225),
            _     => amt + (amt / 6.735)
        };

        private void btnEvaluateWaterBill_Click(object sender, EventArgs e)
        {
            double counterStart = 0, counterEnd = 0;

            try
            {
                counterStart = double.Parse(txtCounterReadingStart.Text);
            }
            catch (FormatException feCRStart)
            {
                MessageBox.Show("There was a problem with the value of the " +
                                "Counter Reading Start. The error produced is: " + feCRStart.Message,
                                "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }

            try
            {
                counterEnd = double.Parse(txtCounterReadingEnd.Text);
            }
            catch (FormatException feCREnd)
            {
                MessageBox.Show("There was a problem with the value of the " +
                                "Counter Reading End. The error produced is: " + feCREnd.Message,
                                "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }

            double consumption            = counterEnd - counterStart;
            double gallons                = consumption * 748.05;

            string strAccountType         = txtAccountType.Text[..3];

            (double first, double second, double last) tiers = CalculateTiers(strAccountType, gallons);

            double waterCharges           = tiers.first + tiers.second + tiers.last;
            double sewerCharges           = CalculateSewerCharges(strAccountType, waterCharges);
            double envCharges             = CalculateEnvironmentCharges(strAccountType, waterCharges);
            double srvCharges             = CalculateServiceCharges(strAccountType, waterCharges);
            double totalCharges           = waterCharges + sewerCharges + envCharges + srvCharges;
            double localTaxes             = CalculateLocalTaxes(strAccountType, waterCharges);
            double stateTaxes             = CalculateStateTaxes(strAccountType, waterCharges);
            double amtDue                 = totalCharges + localTaxes + stateTaxes;

            txtTotalHCF.Text              = consumption.ToString();
            txtTotalGallons.Text          = ((int)(Math.Ceiling(gallons))).ToString();
            txtFirstTierConsumption.Text  = tiers.first.ToString("F");
            txtSecondTierConsumption.Text = tiers.second.ToString("F");
            txtLastTierConsumption.Text   = tiers.last.ToString("F");
            txtWaterCharges.Text          = waterCharges.ToString("F");
            txtSewerCharges.Text          = sewerCharges.ToString("F");
            txtEnvironmentCharges.Text    = envCharges.ToString("F");
            txtServiceCharges.Text        = srvCharges.ToString("F");
            txtTotalCharges.Text          = totalCharges.ToString("F");
            txtLocalTaxes.Text            = localTaxes.ToString("F");
            txtStateTaxes.Text            = stateTaxes.ToString("F");
            dtpPaymentDueDate.Value       = SetPaymentDueDate(strAccountType, dtpMeterReadingEndDate.Value);
            txtAmountDue.Text             = amtDue.ToString("F");
            dtpLatePaymentDueDate.Value   = SetLatePaymentDueDate(strAccountType, dtpMeterReadingEndDate.Value);
            txtLateAmountDue.Text         = CalculateLateAmountDue(strAccountType, amtDue).ToString("F");
        }
    }
}

Return to the Water Bills - Create form and double-click the Save Water Bill button
Return to the form and double-click the Close button

Finalize the document as follows:

using System.Xml;

namespace StellarWaterPoint3.WaterBills
{
    public partial class Create : Form
    {
        public Create()
        {
            InitializeComponent();
        }

        private void btnFindCustomerAccount_Click(object sender, EventArgs e)
        {
            XmlDocument xdCustomers = new XmlDocument();
            string? strCustomers    = @"C:\Stellar Water Point6\Customers.xml";

            FileInfo? fiCustomers   = new FileInfo(strCustomers);

            string strMeterNumber   = string.Empty;

            if (fiCustomers.Exists)
            {
                using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdCustomers.Load(fsCustomers);
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + mtbAccountNumber.Text + "']")!;

                    foreach (XmlNode xnCustomer in xnlCustomers)
                    {
                        txtAccountName.Text = xnCustomer.NextSibling!.InnerText;
                        strMeterNumber      = xnCustomer.NextSibling.NextSibling!.InnerText;
                        txtAccountType.Text = xnCustomer.NextSibling.NextSibling.NextSibling!.InnerText;
                        txtAddress.Text     = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;
                        txtCity.Text        = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;
                        txtCounty.Text      = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtState.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtZIPCode.Text     = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                    }
                }
            }

            XmlDocument xdWaterMeters = new XmlDocument();
            string? strWaterMeters = @"C:\Stellar Water Point6\WaterMeters.xml";

            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            if (fiWaterMeters.Exists)
            {
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterMeters.Load(fsWaterMeters);
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                    }
                }
            }
        }

        private void dtpMeterReadingEndDate_ValueChanged(object sender, EventArgs e)
        {
            TimeSpan tsDays = dtpMeterReadingEndDate.Value - dtpMeterReadingStartDate.Value;

            txtBillingDays.Text = (tsDays.Days + 1).ToString();
        }

        (double a, double b, double c) CalculateTiers(string acnt, double total)
        {
            (double tier1, double tier2, double tier3) results = (0.00, 0.00, 0.00);

            if (acnt == "RES")
            {
                results.tier1 = total * 41.50 / 10000.00;
                results.tier2 = total * 32.50 / 10000.00;
                results.tier3 = total * 26.00 / 10000.00;
            }
            else if (acnt == "SGO")
            {
                results.tier1 = total * 46 / 10000;
                results.tier2 = total * 50 / 10000;
                results.tier3 = total *  4 / 10000;
            }
            else if (acnt == "BUS")
            {
                results.tier1 = total * 45 / 10000;
                results.tier2 = total * 30 / 10000;
                results.tier3 = total * 25 / 10000;
            }
            else if (acnt == "UUO")
            {
                results.tier1 = total * 25 / 10000;
                results.tier2 = total * 35 / 10000;
                results.tier3 = total * 40 / 10000;
            }
            else if (acnt == "WAT")
            {
                results.tier1 = total * 50 / 10000;
                results.tier2 = total * 40 / 10000;
                results.tier3 = total * 10 / 10000;
            }
            else
            {
                results.tier1 = total * (48.00 / 10000.00);
                results.tier2 = total * (32.00 / 10000.00);
                results.tier3 = total * (20.00 / 10000.00);
            }

            return results;
        }

        private double CalculateSewerCharges(string acnt, double total)
        {
            double result;

            if (acnt == "RES")
            {
                result = total * 6.826941 / 100;
            }
            else if (acnt == "SGO")
            {
                result = total * 4.162522 / 100;
            }
            else if (acnt == "BUS")
            {
                result = total * 8.3136 / 100;
            }
            else if (acnt == "UUO")
            {
                result = total * 10.6247 / 100;
            }
            else if (acnt == "WAT")
            {
                result = total * 12.0535 / 100;
            }
            else // if (acnt == "OTH)"
            {
                result = total * 9.2065 / 100;
            }

            return result;
        }

        private double CalculateEnvironmentCharges(string acnt, double total)
        {
            double result;

            switch(acnt)
            {
                case "RES":
                    result = total * 0.022724;
                    break;
                case "SGO":
                    result = total * 0.118242;
                    break;
                case "BUS":
                    result = total * 0.161369;
                    break;
                case "UUO":
                    result = total * 0.082477;
                    break;
                case "WAT":
                    result = total * 0.413574;
                    break;
                default:
                    result = total * 0.221842;
                    break;
            }

            return result;
        }

        private double CalculateServiceCharges(string acnt, double total)
        {
            switch (acnt)
            {
                case "RES":
                    return total * 0.145748;
                case "SGO":
                    return total * 0.102246;
                case "BUS":
                    return total * 0.242627;
                case "UUO":
                    return total * 0.186692;
                case "WAT":
                    return total * 0.412628;
                default:
                    return total * 0.210248;
            }
        }

        private double CalculateLocalTaxes(string acnt, double total) => acnt switch
        {
            "RES" => total * 0.031574,
            "SGO" => total * 0.035026,
            "BUS" => total * 0.122517,
            "UUO" => total * 0.105737,
            "WAT" => total * 0.153248,
            _ => total * 0.125148
        };

        private double CalculateStateTaxes(string acnt, double total) => acnt switch
        {
            "RES" => total * 0.016724,
            "SGO" => total * 0.008779,
            "BUS" => total * 0.042448,
            "UUO" => total * 0.067958,
            "WAT" => total * 0.081622,
            _ => total * 0.013746
        };

        private DateTime SetPaymentDueDate(string acnt, DateTime date)
        {
            TimeSpan tsPaymentDueDate = new TimeSpan(1, 0, 0, 0);

            if (acnt == "RES")
            {
                tsPaymentDueDate = new TimeSpan(15, 0, 0, 0);
            }
            else if (acnt == "SGO")
            {
                tsPaymentDueDate = new TimeSpan(20, 0, 0, 0);
            }
            else if (acnt == "BUS")
            {
                tsPaymentDueDate = new TimeSpan(30, 0, 0, 0);
            }
            else if (acnt == "UUO")
            {
                tsPaymentDueDate = new TimeSpan(15, 0, 0, 0);
            }
            else if (acnt == "WAT")
            {
                tsPaymentDueDate = new TimeSpan(40, 0, 0, 0);
            }
            else
            {
                tsPaymentDueDate = new TimeSpan(35, 0, 0, 0);
            }

            return date + tsPaymentDueDate;
        }

        private DateTime SetLatePaymentDueDate(string acnt, DateTime date)
        {
            switch (acnt)
            {
                case "RES":
                    return date + new TimeSpan(30, 0, 0, 0);
                case "SGO":
                    return date + new TimeSpan(40, 0, 0, 0);
                case "BUS":
                    return date + new TimeSpan(50, 0, 0, 0);
                case "UUO":
                    return date + new TimeSpan(60, 0, 0, 0);
                case "WAT":
                    return date + new TimeSpan(65, 0, 0, 0);
                default:
                    return date + new TimeSpan(45, 0, 0, 0);
            }
        }

        private double CalculateLateAmountDue(string acnt, double amt) => acnt switch
        {
            "RES" => amt + 8.95,
            "SGO" => amt + (amt / 4.575),
            "BUS" => amt + (amt / 12.315),
            "UUO" => amt + (amt / 7.425),
            "WAT" => amt + (amt / 15.225),
            _     => amt + (amt / 6.735)
        };

        private void btnEvaluateWaterBill_Click(object sender, EventArgs e)
        {
            double counterStart = 0, counterEnd = 0;

            try
            {
                counterStart = double.Parse(txtCounterReadingStart.Text);
            }
            catch (FormatException feCRStart)
            {
                MessageBox.Show("There was a problem with the value of the " +
                                "Counter Reading Start. The error produced is: " + feCRStart.Message,
                                "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }

            try
            {
                counterEnd = double.Parse(txtCounterReadingEnd.Text);
            }
            catch (FormatException feCREnd)
            {
                MessageBox.Show("There was a problem with the value of the " +
                                "Counter Reading End. The error produced is: " + feCREnd.Message,
                                "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }

            double consumption            = counterEnd - counterStart;
            double gallons                = consumption * 748.05;

            string strAccountType         = txtAccountType.Text[..3];

            (double first, double second, double last) tiers = CalculateTiers(strAccountType, gallons);

            double waterCharges           = tiers.first + tiers.second + tiers.last;
            double sewerCharges           = CalculateSewerCharges(strAccountType, waterCharges);
            double envCharges             = CalculateEnvironmentCharges(strAccountType, waterCharges);
            double srvCharges             = CalculateServiceCharges(strAccountType, waterCharges);
            double totalCharges           = waterCharges + sewerCharges + envCharges + srvCharges;
            double localTaxes             = CalculateLocalTaxes(strAccountType, waterCharges);
            double stateTaxes             = CalculateStateTaxes(strAccountType, waterCharges);
            double amtDue                 = totalCharges + localTaxes + stateTaxes;

            txtTotalHCF.Text              = consumption.ToString();
            txtTotalGallons.Text          = ((int)(Math.Ceiling(gallons))).ToString();
            txtFirstTierConsumption.Text  = tiers.first.ToString("F");
            txtSecondTierConsumption.Text = tiers.second.ToString("F");
            txtLastTierConsumption.Text   = tiers.last.ToString("F");
            txtWaterCharges.Text          = waterCharges.ToString("F");
            txtSewerCharges.Text          = sewerCharges.ToString("F");
            txtEnvironmentCharges.Text    = envCharges.ToString("F");
            txtServiceCharges.Text        = srvCharges.ToString("F");
            txtTotalCharges.Text          = totalCharges.ToString("F");
            txtLocalTaxes.Text            = localTaxes.ToString("F");
            txtStateTaxes.Text            = stateTaxes.ToString("F");
            dtpPaymentDueDate.Value       = SetPaymentDueDate(strAccountType, dtpMeterReadingEndDate.Value);
            txtAmountDue.Text             = amtDue.ToString("F");
            dtpLatePaymentDueDate.Value   = SetLatePaymentDueDate(strAccountType, dtpMeterReadingEndDate.Value);
            txtLateAmountDue.Text         = CalculateLateAmountDue(strAccountType, amtDue).ToString("F");
        }

        private void btnSaveWaterBill_Click(object sender, EventArgs e)
        {
            if (string.IsNullOrEmpty(txtBillNumber.Text))
            {
                MessageBox.Show("You must type a bill number." +
                                "Otherwise, the account cannot be saved.",
                                "Stellar Water Point", MessageBoxButtons.OK);
                return;
            }

            if (string.IsNullOrEmpty(txtCounterReadingStart.Text))
            {
                MessageBox.Show("You must enter the start value of the water bill counter." +
                                "Otherwise, the account cannot be saved.",
                                "Stellar Water Point", MessageBoxButtons.OK);
                return;
            }

            if (string.IsNullOrEmpty(mtbAccountNumber.Text))
            {
                MessageBox.Show("You must type an account number of a customer." +
                                "Otherwise, the account cannot be saved.",
                                "Stellar Water Point", MessageBoxButtons.OK);
                return;
            }

            FileStream? fsWaterBills = null;
            XmlDocument xdWaterBills = new XmlDocument();
            string strWaterBills     = @"C:\Stellar Water Point6\WaterBills.xml";

            FileInfo? fiWaterBills   = new FileInfo(strWaterBills);

            if (fiWaterBills.Exists)
            {
                using (fsWaterBills = new FileStream(fiWaterBills.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterBills.Load(fsWaterBills);
                }
            }
            else
            {
                using (fsWaterBills = new FileStream(fiWaterBills.FullName, FileMode.Create, FileAccess.Write, FileShare.Write))
                {
                    xdWaterBills.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                                         "<water-bills></water-bills>");
                    xdWaterBills.Save(fsWaterBills);
                }
            }

            using (fsWaterBills = new FileStream(fiWaterBills.FullName, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite))
            {
                XmlElement xeWaterBill = xdWaterBills.CreateElement("water-bill");

                xeWaterBill.InnerXml = "<bill-number>"              + txtBillNumber.Text + "</bill-number>" +
                                       "<account-number>"           + mtbAccountNumber.Text + "</account-number>" +
                                       "<meter-reading-start-date>" + dtpMeterReadingStartDate.Value.ToShortDateString() + "</meter-reading-start-date>" +
                                       "<meter-reading-end-date>"   + dtpMeterReadingEndDate.Value.ToShortDateString() + "</meter-reading-end-date>" +
                                       "<billing-days>"             + txtBillingDays.Text + "</billing-days>" +
                                       "<counter-reading-start>"    + txtCounterReadingStart.Text + "</counter-reading-start>" +
                                       "<counter-reading-end>"      + txtCounterReadingEnd.Text + "</counter-reading-end>" +
                                       "<total-hcf>"                + txtTotalHCF.Text + "</total-hcf>" +
                                       "<total-gallons>"            + txtTotalGallons.Text + "</total-gallons>" +
                                       "<first-tier-consumption>"   + txtFirstTierConsumption.Text + "</first-tier-consumption>" +
                                       "<second-tier-consumption>"  + txtSecondTierConsumption.Text + "</second-tier-consumption>" +
                                       "<last-tier-consumption>"    + txtLastTierConsumption.Text + "</last-tier-consumption>" +
                                       "<water-charges>"            + txtWaterCharges.Text + "</water-charges>" +
                                       "<sewer-charges>"            + txtSewerCharges.Text + "</sewer-charges>" +
                                       "<environment-charges>"      + txtEnvironmentCharges.Text + "</environment-charges>" +
                                       "<service-charges>"          + txtEnvironmentCharges.Text + "</service-charges>" +
                                       "<total-charges>"            + txtTotalCharges.Text + "</total-charges>" +
                                       "<state-taxes>"              + txtStateTaxes.Text + "</state-taxes>" +
                                       "<local-taxes>"              + txtLocalTaxes.Text + "</local-taxes>" +
                                       "<payment-due-date>"         + dtpPaymentDueDate.Value.ToShortDateString() + "</payment-due-date>" +
                                       "<amount-due>"               + txtAmountDue.Text + "</amount-due>" +
                                       "<late-payment-due-date>"    + dtpLatePaymentDueDate.Value.ToShortDateString() + "</late-payment-due-date>" +
                                       "<late-amount-due>"          + txtLateAmountDue.Text + "</late-amount-due>";

                xdWaterBills.DocumentElement!.AppendChild(xeWaterBill);
                xdWaterBills.Save(fsWaterBills);
            }

            Close();
        }

        private void btnClose_Click(object sender, EventArgs e)
        {
            Close();
        }
    }
}

A List of Water Bills

Practical Learning: Viewing Water Bills

To create a form, in the Solution Explorer, right-click WaterBills -> Add -> Form (Windows Forms)...
Type Central
Click Add
In the Toolbox, click the ListView button and click the form

In the Properties window, change the characteristics of the list view as follows:

Control	(Name)	Text	Other Properties
ListView	lvwWaterBills		FullRowSelect: True GridLines: True View: Details Anchor: Top, Bottom, Left, Right
Button	btnCreateWaterBill	Close	&Create Water Bill...

On the form, right-click the list view and click Edit Columns...

Create the columns as follows:

(Name)	Text	TextAlign	Width
colWaterBillId	Id		40
colBillNumber	Bill #	Center	80
colAccountNumber	Account #	Center	150
colStartDate	Start Date	Center	150
colEndDate	End Date	Center	150
colBillingDays	Days	Center
colCounterStart	Counter Start	Right	125
colCounterEnd	Counter End	Right	125
colTotalHCF	Total HCF	Right	100
colGallons	Gallons	Right	80
colPaymentDueDate	Pmt Due Date	Center	125
colAmountDue	Amt Due	Right	90

Click OK
Doubte-click an unoccupied area of the form to generate its Load event

Change the document as follows:

using System.Xml;

namespace StellarWaterPoint3.WaterBills
{
    public partial class Central : Form
    {
        public Central()
        {
            InitializeComponent();
        }

        private void ShowWaterBills()
        {
            lvwWaterBills.Items.Clear();

            XmlDocument xdWaterBills = new XmlDocument();
            string? strWaterBills = @"C:\Stellar Water Point6\WaterBills.xml";

            FileInfo? fiWaterBills = new FileInfo(strWaterBills);

            if (fiWaterBills.Exists)
            {
                using (FileStream? fsWaterBills = new FileStream(fiWaterBills.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterBills.Load(fsWaterBills);
                    XmlNodeList xnlWaterBills = xdWaterBills.DocumentElement!.ChildNodes;

                    int i = 1;

                    foreach (XmlNode xnWaterBill in xnlWaterBills)
                    {
                        ListViewItem lviWaterBill = new ListViewItem(i.ToString());

                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild!.InnerText);
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling!.InnerText);
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling!.InnerText);
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling!.InnerText);
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText);
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText);
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText);
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText);
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText.ToString());
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText);
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText);

                        lvwWaterBills.Items.Add(lviWaterBill);

                        i++;
                    }
                }
            }
        }

        private void Central_Load(object sender, EventArgs e)
        {
            ShowWaterBills();
        }
    }
}

Return to the Water Bills form and double-click the Create Water Bill button

Implement the event as follows:

using System.Xml;

namespace StellarWaterPoint3.WaterBills
{
    public partial class Central : Form
    {
        public Central()
        {
            InitializeComponent();
        }

        private void ShowWaterBills()
        {
            lvwWaterBills.Items.Clear();

            XmlDocument xdWaterBills = new XmlDocument();
            string? strWaterBills = @"C:\Stellar Water Point6\WaterBills.xml";

            FileInfo? fiWaterBills = new FileInfo(strWaterBills);

            if (fiWaterBills.Exists)
            {
                using (FileStream? fsWaterBills = new FileStream(fiWaterBills.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterBills.Load(fsWaterBills);
                    XmlNodeList xnlWaterBills = xdWaterBills.DocumentElement!.ChildNodes;

                    int i = 1;

                    foreach (XmlNode xnWaterBill in xnlWaterBills)
                    {
                        ListViewItem lviWaterBill = new ListViewItem(i.ToString());

                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild!.InnerText);   // Water Bill #
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling!.InnerText);   // Account Number
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling!.InnerText); // Meter Reading Start Date
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling!.InnerText);   // Meter Reading End Date
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText); // Billing Days
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText);  // Counter Reading Start
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText);   // Counter Reading End
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText);   // Total CCF
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText.ToString());   // Gallons
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText);   // Payment Due Date
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText);  // Amount Due

                        lvwWaterBills.Items.Add(lviWaterBill);

                        i++;
                    }
                }
            }
        }

        private void Central_Load(object sender, EventArgs e)
        {
            ShowWaterBills();
        }

        private void btnCreateWaterBill_Click(object sender, EventArgs e)
        {
            Create create = new();

            create.ShowDialog();

            ShowWaterBills();
        }
    }
}

In the Solution Explorer, double-click WaterDistribution.cs to open the main form of the application
From the Toolbox, add a button to the form

Using the the Properties window, change the characteristics of the button as follows:

Control	(Name)	Text	Font
Button	btnWaterBills	Water &Bills...	Times New Roman, 24pt, style=Bold
Button	btnClose	&Close	Times New Roman, 24pt, style=Bold

Double-click the Water &Bills button
Return to the Water Distribution form and double-click the Close button

Change the document as follows:

namespace StellarWaterPoint3
{
    public partial class WaterDistribution : Form
    {
        public WaterDistribution()
        {
            InitializeComponent();
        }

        private void WaterDistribution_Load(object sender, EventArgs e)
        {
            // If the directory for the database doesn't yet exist, create it
            Directory.CreateDirectory(@"C:\Stellar Water Point6");
        }

        private void btnCustomers_Click(object sender, EventArgs e)
        {
            Customers.Central central = new Customers.Central();

            central.ShowDialog();
        }

        private void btnWaterMeters_Click(object sender, EventArgs e)
        {
            WaterMeters.Central central = new WaterMeters.Central();

            central.ShowDialog();
        }

        private void btnWaterBills_Click(object sender, EventArgs e)
        {
            WaterBills.Central central = new();

            central.Show();
        }

        private void btnClose_Click(object sender, EventArgs e)
        {
            Close();
        }
    }
}

To execute the application, on the main menu, click Debug -> Start Without Debugging:
On the Water Distribution form, click the Water Bills button:
On the Water Bills form, click the Create Water Bill button:

Enter the following values in the indicated text boxes or select the date values. Then click Find Customer Account, followed by Evaluate Water Bill, followed by Save Water Bill:

Water Bill #	Account #	Reading Start Date	Reading End Date	Counter Reading Start	Counter Reading End
451474	2068-258-9486	01/11/2010	04/12/2010	103943	103956
923633	5293-957-3395	01/17/2010	08/18/2010	256945	256972
917829	9279-570-8394	02/15/2010	05/14/2010	5205	5222
202666	6986-829-3741	03/08/2010	06/06/2010	5679	5690

Close the forms and return to your programming environment

Details on a Wate Bill

Practical Learning: Creating a Water Meter Record

To create a form, in the Solution Explorer, right-click WaterBills -> Add -> Form (Windows Forms)...
For the Name of the form, type Details
Press Enter

Design the form as follows:

Stellar Water Point - New Customer Account

Control	(Name)	Text	Other Properties
Label		Water Bill #:
TextBox	txtBillNumber
Button	btnFindWaterBill	Find Water Bill
GroupBox		Customer Information
Label		Account #:
TextBox	txtAccountNumber		Enabled: False
Label		Customer Name:
TextBox	txtCustomerName		Enabled: False
Label		Address:
TextBox	txtAddress		Enabled: False
TextBox	txtCity		Enabled: False
TextBox	txtCounty		Enabled: False
TextBox	txtState		Enabled: False
TextBox	txtZIPCode		Enabled: False
Label		_____________________________________
Label		Meter Details:
TextBox	txtMeterDetails		Enabled: False
GroupBox		Meter Reading
Label		Meter Reading Start Date:
TextBox	txtMeterReadingStartDate		Enabled: False
Label		Meter Reading End Date:
TextBox	txtMeterReadingEndDate		Enabled: False
Label		Counter Reading Start:
TextBox	txtCounterReadingStart		Enabled: False
Label		Counter Reading End:
TextBox	txtCounterReadingEnd		Enabled: False
GroupBox		Meter Result
Label		Billing Days:
TextBox	txtBillingDays		TextAlign: Right Enabled: False
Label		Total Gallons:
TextBox	txtTotalGallons		TextAlign: Right Enabled: False
Label		Total CCF:
TextBox	txtTotalHCF		TextAlign: Right Enabled: False
Label		First Tier Consumption:
TextBox	txtFirstTierConsumption		TextAlign: Right Enabled: False
Label		Second Tier:
TextBox	txtSecondTierConsumption		TextAlign: Right Enabled: False
Label		Last Tier:
TextBox	txtLastTierConsumption		TextAlign: Right Enabled: False
GroupBox		Consumption Charges
Label		Water Charges:
TextBox	txtWaterCharges		TextAlign: Right Enabled: False
Label		Sewer Charges:
TextBox	txtSewerCharges		TextAlign: Right Enabled: False
Label		Environment Charges:
TextBox	txtEnvironmentCharges		TextAlign: Right Enabled: False
Label		Total Charges:
TextBox	txtTotalCharges		TextAlign: Right Enabled: False
GroupBox		Taxes
Label		Local Taxes:
TextBox	txtLocalTaxes		TextAlign: Right Enabled: False
Label		State Taxes:
TextBox	txtStateTaxes		TextAlign: Right Enabled: False
GroupBox		Water Bill Payment
Label		Payment Due Date:
TextBox	txtPaymentDueDate		Enabled: False
Label		Amount Due:
TextBox	txtAmountDue		TextAlign: Right Enabled: False
Label		Late Payment Due Date:
TextBox	txtLatePaymentDueDate		Enabled: False
Label		Late Amount Due:
TextBox	txtLateAmountDue		TextAlign: Right Enabled: False
Button	btnClose	Close

Using the Properties window, change some characteristics of the form as follows:

FormBorderStyle: FixedDialog
Text:            Stellar Water Point - Water Bill Details
StartPosition:   CenterScreen
MinimizeBox:     False
MaximizeBox:     False

On the form, double-click the Find Water Bill button
Return to the form and double-click the Close button

Change the document as follows:

using System.Xml;

namespace StellarWaterPoint3.WaterBills
{
    public partial class Details : Form
    {
        public Details()
        {
            InitializeComponent();
        }

        private void btnFindWaterBill_Click(object sender, EventArgs e)
        {
            /* If the user clicks the Find Water Meter button, 
             * make sure there is an invoice number in the top text box. */
            if (string.IsNullOrEmpty(txtBillNumber.Text))
            {
                MessageBox.Show("You must provide a water bill number and then click the Find Water Bill button.",
                                "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
                // If the user didn't type a bill number but clicked Find Water Bill, don't do anything
                return;
            }

            XmlDocument xdWaterBills = new XmlDocument();
            string? strWaterBills = @"C:\Stellar Water Point6\WaterBills.xml";

            FileInfo? fiWaterBills = new FileInfo(strWaterBills);

            if (fiWaterBills.Exists)
            {
                using (FileStream? fsWaterBills = new FileStream(fiWaterBills.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterBills.Load(fsWaterBills);

                    /* Use XPath to locate the water bill that has 
                     * the same invoice number as the one in the Water Bill Number text box.
                     * Store the water bill in an XmlNodeList variable. */
                    XmlNodeList xnlWaterBills = xdWaterBills.DocumentElement!.SelectNodes("//bill-number[.='" + txtBillNumber.Text + "']")!;

                    foreach (XmlNode xnWaterBill in xnlWaterBills)
                    {
                        txtBillNumber.Text            =                xnWaterBill.FirstChild!.InnerText;
                        txtAccountNumber.Text         =                xnWaterBill.NextSibling!.InnerText;
                        txtMeterReadingStartDate.Text = DateTime.Parse(xnWaterBill.NextSibling.NextSibling!.InnerText).ToLongDateString();
                        txtMeterReadingEndDate.Text   = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling!.InnerText).ToLongDateString();                        
                        txtBillingDays.Text           =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;
                        txtCounterReadingStart.Text   =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText;                        
                        txtCounterReadingEnd.Text     =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtTotalHCF.Text              =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtTotalGallons.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtFirstTierConsumption.Text  =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtSecondTierConsumption.Text =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtLastTierConsumption.Text   =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtWaterCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtSewerCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtEnvironmentCharges.Text    =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtServiceCharges.Text        =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtTotalCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtStateTaxes.Text            =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtLocalTaxes.Text            =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtPaymentDueDate.Text        = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText).ToLongDateString();
                        txtAmountDue.Text             =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtLatePaymentDueDate.Text    = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText).ToLongDateString();
                        txtLateAmountDue.Text         =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                    }
                }
            }

            XmlDocument xdCustomers = new XmlDocument();
            // Declare a variable for a file that holds the list of customers
            string? strCustomers = @"C:\Stellar Water Point6\Customers.xml";

            // Create a FileInfo object for the customers
            FileInfo? fiCustomers = new FileInfo(strCustomers);

            // We will need to know the water meter associated with this customer account
            string strMeterNumber = string.Empty;

            // Check whether the file that holds a list of customers exists
            if (fiCustomers.Exists)
            {
                // If that exists, open it and pass it to a FileStream object
                using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    // Get the list of customers and pass the records to the XML DOM object created earlier
                    xdCustomers.Load(fsCustomers);
                    // Create an XmlNodeList list of customers using XPath
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + txtAccountNumber.Text + "']")!;

                    // Check each node of the XML record and display its values in each Windows control on the form
                    foreach (XmlNode xnCustomer in xnlCustomers)
                    {
                        //mtbAccountNumber.Text = xnCustomer.NextSibling!.InnerText;   // Meter #
                        txtAccountName.Text = xnCustomer.NextSibling!.InnerText; // Account Name

                        strMeterNumber      = xnCustomer.NextSibling.NextSibling!.InnerText;   // Meter Number
                        txtAccountType.Text = xnCustomer.NextSibling.NextSibling.NextSibling!.InnerText;   // Account Type
                        txtAddress.Text     = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // Address
                        txtCity.Text        = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // City
                        txtCounty.Text      = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;   // County
                        txtState.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;   // State
                        txtZIPCode.Text     = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText; // ZIP-Code
                    }
                }
            }

            // Create an XML DOM object for the water meters records
            XmlDocument xdWaterMeters = new XmlDocument();
            // Declare a variable for a file that holds the list of water meters
            string? strWaterMeters = @"C:\Stellar Water Point6\WaterMeters.xml";

            // Create a FileInfo object for the customers
            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            // Check whether the file that holds a list of water meters exists
            if (fiWaterMeters.Exists)
            {
                // Get the list of water meters and pass the records to the XML DOM object
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    // Get the list of water meters and pass the records to the XML DOM object
                    xdWaterMeters.Load(fsWaterMeters);
                    // Create an XmlNodeList list of water meters using XPath
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    // Check each node of the XML record
                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        /* Get the values for the water meter.
                         * Create a sentence and display it in the Meter Details text box. */
                        txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                    }
                }
            }
        }

        private void btnClose_Click(object sender, EventArgs e)
        {
            Close();
        }
    }
}

In the Solution Explorer, below the WaterBills folder, double-click Details.cs to open its form
From the Toolbox, add a button to the form below the list view and to the right of the Create Water Bill button

Change the characteristics of the button as follows:

Control		(Name)	Other Properties
Button		btnViewWaterBill	&View Water Bill... Anchor: Bottom, Right

Double-click the View Water Bill button

Change the document as follows:

using System.Xml;

namespace StellarWaterPoint3.WaterBills
{
    public partial class Central : Form
    {
        public Central()
        {
            InitializeComponent();
        }

        private void ShowWaterBills()
        {
            . . .
        }

        private void Central_Load(object sender, EventArgs e)
        {
            ShowWaterBills();
        }

        private void btnCreateWaterBill_Click(object sender, EventArgs e)
        {
            Create create = new();

            create.ShowDialog();

            ShowWaterBills();
        }

        private void btnViewWaterBill_Click(object sender, EventArgs e)
        {
            Details details = new();

            details.ShowDialog();
        }
    }
}

To execute the application, on the main menu, click Debug -> Start Without Debugging
On the Water Distribution form, click the Water Bills button:
On the Water Bills form, click the View Water Bill button:
In the Water Bill # text box, type 917829
Click the Find Water Bill button:
Close the Details form
Close the forms and return to your programming environment

Water Bill Edition

Practical Learning: Editing a Water Bill

To create a new form, in the Solution Explorer, right-click Water Bills -> New -> Form (Windows Forms)...
Type Editor as the name of the form
Click Add
Make that form the same size as the Create Water Bill form
Select everything on the Create Water Bill form. Copy that selection and paste it in the new Water Bill Editor form
Copy the Find Water Bill button from the Water Bill Details form and paste it on the Water Bill Editor form

Complete the design of the form as follows:

Control	(Name)	Text	Other Properties
Label		Water Bill #:
TextBox	txtBillNumber		Modifiers: Public
Button	btnFindWaterBill	&Find Water Bill
GroupBox		Customer Information
Label		Account #:
MaskedTextBox	mtbAccountNumber		Masked: 0000-000-0000 Modifiers: Public
Button	btnFindCustomerAccount	Find Customer Account
Label		Account Name:
TextBox	txtAccountName		Enabled: False
Label		Address:
TextBox	txtAddress		Enabled: False
TextBox	txtCity		Enabled: False
TextBox	txtCounty		Enabled: False
TextBox	txtState		Enabled: False
TextBox	mtbZIPCode		Enabled: False
Label		______________________________________________
Label		Meter Details:
TextBox	txtMeterDetails		Modifiers: Public
GroupBox		Meter Reading
Label		Meter Reading Start Date:
DateTimePicker	dtpMeterReadingStartDate		Modifiers: Public
Label		Meter Reading End Date:
DateTimePicker	dtpMeterReadingEndDate		Modifiers: Public
Label		Counter Reading Start:
TextBox	txtCounterReadingStart		Modifiers: Public
Label		Counter Reading End:
TextBox	txtCounterReadingEnd		Modifiers: Public
Button	btnEvaluateWaterBill	Evaluate Water Bill
GroupBox		Meter Result
Label		Billing Days:
TextBox	txtBillingDays		TextAlign: Right Modifiers: Public
Label		Total Gallons:
TextBox	txtTotalGallons		TextAlign: Right Modifiers: Public
Label		Total CCF:
TextBox	txtTotalCCF		TextAlign: Right Modifiers: Public
Label		First Tier Consumption:
TextBox	txtFirstTierConsumption		TextAlign: Right Modifiers: Public
Label		Second Tier:
TextBox	txtSecondTierConsumption		TextAlign: Right Modifiers: Public
Label		Last Tier:
TextBox	txtLastTierConsumption		TextAlign: Right Modifiers: Public
GroupBox		Consumption Charges
Label		Water Charges:
TextBox	txtWaterCharges		TextAlign: Right Modifiers: Public
Label		Sewer Charges:
TextBox	txtSewerCharges		TextAlign: Right Modifiers: Public
Label		Environment Charges:
TextBox	txtEnvironmentCharges		TextAlign: Right Modifiers: Public
Label		Total Charges:
TextBox	txtTotalCharges		TextAlign: Right Modifiers: Public
GroupBox		Taxes
Label		Local Taxes:
TextBox	txtLocalTaxes		TextAlign: Right Modifiers: Public
Label		State Taxes:
TextBox	txtStateTaxes		TextAlign: Right Modifiers: Public
GroupBox		Water Bill Payment
Label		Payment Due Date:
DateTimePicker	dtpPaymentDueDate		Modifiers: Public
Label		Amount Due:
TextBox	txtAmountDue		TextAlign: Right Modifiers: Public
Label		Late Payment Due Date:
DateTimePicker	dtpLatePaymentDueDate		Modifiers: Public
Label		Late Amount Due:
TextBox	txtLateAmountDue		TextAlign: Right Modifiers: Public
Button	btnUpdateWaterBill	Update Water Bill	DialogResult: OK
Button	btnClose	Close	DialogResult: Cancel

Using the Properties window, change some characteristics of the form as follows:

FormBorderStyle: FixedDialog
Text:            Stellar Water Point - Water Bill Edition
StartPosition:   CenterScreen
MinimizeBox:     False
MaximizeBox:     False
AcceptButton:    btnUpdateWaterBill
CancelButton:    btnClose

On the form, double-click the Find Water Bill button

Change the document as follows:

using System.Xml;using System.Xml;
{
    public partial class Editor : Form
    {
        public Editor()
        {
            InitializeComponent();
        }

        private void btnFindWaterBill_Click(object sender, EventArgs e)
        {
            if (string.IsNullOrEmpty(txtBillNumber.Text))
            {
                MessageBox.Show("You must provide a water bill number and then click the Find Water Bill button.",
                                "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
                return;
            }

            XmlDocument xdWaterBills = new XmlDocument();
            string? strWaterBills = @"C:\Stellar Water Point6\WaterBills.xml";

            FileInfo? fiWaterBills = new FileInfo(strWaterBills);

            if (fiWaterBills.Exists)
            {
                using (FileStream? fsWaterBills = new FileStream(fiWaterBills.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterBills.Load(fsWaterBills);

                    XmlNodeList xnlWaterBills = xdWaterBills.DocumentElement!.SelectNodes("//bill-number[.='" + txtBillNumber.Text + "']")!;

                    foreach (XmlNode xnWaterBill in xnlWaterBills)
                    {
                        txtBillNumber.Text            =                xnWaterBill.FirstChild!.InnerText;
                        mtbAccountNumber.Text         =                xnWaterBill.NextSibling!.InnerText;
                        dtpMeterReadingStartDate.Text = DateTime.Parse(xnWaterBill.NextSibling.NextSibling!.InnerText).ToLongDateString();
                        dtpMeterReadingEndDate.Text   = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling!.InnerText).ToLongDateString();
                        txtBillingDays.Text           =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;
                        txtCounterReadingStart.Text   =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText;
                        txtCounterReadingEnd.Text     =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtTotalHCF.Text              =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtTotalGallons.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtFirstTierConsumption.Text  =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtSecondTierConsumption.Text =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtLastTierConsumption.Text   =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtWaterCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtSewerCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtEnvironmentCharges.Text    =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtServiceCharges.Text        =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtTotalCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtStateTaxes.Text            =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtLocalTaxes.Text            =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        dtpPaymentDueDate.Text        = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText).ToLongDateString();
                        txtAmountDue.Text             =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        dtpLatePaymentDueDate.Text    = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText).ToLongDateString();
                        txtLateAmountDue.Text         =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                    }
                }
            }

            XmlDocument xdCustomers = new XmlDocument();
            string? strCustomers = @"C:\Stellar Water Point6\Customers.xml";

            FileInfo? fiCustomers = new FileInfo(strCustomers);

            string strMeterNumber = string.Empty;

            if (fiCustomers.Exists)
            {
                using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdCustomers.Load(fsCustomers);
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + mtbAccountNumber.Text + "']")!;

                    foreach (XmlNode xnCustomer in xnlCustomers)
                    {
                        txtAccountName.Text = xnCustomer.NextSibling!.InnerText; // Account Name

                        strMeterNumber = xnCustomer.NextSibling.NextSibling!.InnerText;   // Meter Number
                        txtAccountType.Text = xnCustomer.NextSibling.NextSibling.NextSibling!.InnerText;   // Account Type
                        txtAddress.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // Address
                        txtCity.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // City
                        txtCounty.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;   // County
                        txtState.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;   // State
                        txtZIPCode.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText; // ZIP-Code
                    }
                }
            }

            XmlDocument xdWaterMeters = new XmlDocument();
            string? strWaterMeters = @"C:\Stellar Water Point6\WaterMeters.xml";

            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            if (fiWaterMeters.Exists)
            {
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterMeters.Load(fsWaterMeters);
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    // Check each node of the XML record
                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                    }
                }
            }
        }
    }
}

Return to the Water Bill - Editor form and double-click the Find Customer Account button

Implement the event as follows:

using System.Xml;

namespace StellarWaterPoint3.WaterBills
{
    public partial class Editor : Form
    {
        public Editor()
        {
            InitializeComponent();
        }

        private void btnFindWaterBill_Click(object sender, EventArgs e)
        {
            . . .
        }

        private void btnFindCustomerAccount_Click(object sender, EventArgs e)
        {
            XmlDocument xdCustomers = new XmlDocument();
            string? strCustomers = @"C:\Stellar Water Point6\Customers.xml";

            FileInfo? fiCustomers = new FileInfo(strCustomers);

            string strMeterNumber = string.Empty;

            if (fiCustomers.Exists)
            {
                using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdCustomers.Load(fsCustomers);
                    XmlNodeList xnlCustomers   = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + mtbAccountNumber.Text + "']")!;

                    foreach (XmlNode xnCustomer in xnlCustomers)
                    {
                        txtAccountName.Text    = xnCustomer.NextSibling!.InnerText;
                        strMeterNumber         = xnCustomer.NextSibling.NextSibling!.InnerText;
                        txtAccountType.Text    = xnCustomer.NextSibling.NextSibling.NextSibling!.InnerText;
                        txtAddress.Text        = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;
                        txtCity.Text           = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;
                        txtCounty.Text         = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtState.Text          = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtZIPCode.Text        = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                    }
                }
            }

            XmlDocument xdWaterMeters = new XmlDocument();
            string? strWaterMeters = @"C:\Stellar Water Point6\WaterMeters.xml";

            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            if (fiWaterMeters.Exists)
            {
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterMeters.Load(fsWaterMeters);
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                    }
                }
            }
        }
    }
}

Return to the Water Bill - Editor form and double-click the Meter Reading End Date date time picker

Implement the event as follows:

using System.Xml;

namespace StellarWaterPoint3.WaterBills
{
    public partial class Editor : Form
    {
        public Editor()
        {
            InitializeComponent();
        }

        private void btnFindWaterBill_Click(object sender, EventArgs e)
        {
            . . .
        }

        private void btnFindCustomerAccount_Click(object sender, EventArgs e)
        {
            . . .
        }

        private void dtpMeterReadingEndDate_ValueChanged(object sender, EventArgs e)
        {
            TimeSpan tsDays = dtpMeterReadingEndDate.Value - dtpMeterReadingStartDate.Value;

            txtBillingDays.Text = (tsDays.Days + 1).ToString();
        }
    }
}

Return to the Water Bill - Editor form and double-click the Re-Evaluate Water Bill button

Implement the event as follows:

using System.Xml;

namespace StellarWaterPoint3.WaterBills
{
    public partial class Editor : Form
    {
        public Editor()
        {
            InitializeComponent();
        }

        private void btnFindWaterBill_Click(object sender, EventArgs e)
        {
            if (string.IsNullOrEmpty(txtBillNumber.Text))
            {
                MessageBox.Show("You must provide a water bill number and then click the Find Water Bill button.",
                                "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
                return;
            }

            XmlDocument xdWaterBills = new XmlDocument();
            string? strWaterBills = @"C:\Stellar Water Point6\WaterBills.xml";

            FileInfo? fiWaterBills = new FileInfo(strWaterBills);

            if (fiWaterBills.Exists)
            {
                using (FileStream? fsWaterBills = new FileStream(fiWaterBills.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterBills.Load(fsWaterBills);

                    XmlNodeList xnlWaterBills = xdWaterBills.DocumentElement!.SelectNodes("//bill-number[.='" + txtBillNumber.Text + "']")!;

                    foreach (XmlNode xnWaterBill in xnlWaterBills)
                    {
                        txtBillNumber.Text            =                xnWaterBill.FirstChild!.InnerText;
                        mtbAccountNumber.Text         =                xnWaterBill.NextSibling!.InnerText;
                        dtpMeterReadingStartDate.Text = DateTime.Parse(xnWaterBill.NextSibling.NextSibling!.InnerText).ToLongDateString();
                        dtpMeterReadingEndDate.Text   = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling!.InnerText).ToLongDateString();
                        txtBillingDays.Text           =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;
                        txtCounterReadingStart.Text   =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText;
                        txtCounterReadingEnd.Text     =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtTotalHCF.Text              =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtTotalGallons.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtFirstTierConsumption.Text  =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtSecondTierConsumption.Text =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtLastTierConsumption.Text   =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtWaterCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtSewerCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtEnvironmentCharges.Text    =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtServiceCharges.Text        =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtTotalCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtStateTaxes.Text            =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtLocalTaxes.Text            =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        dtpPaymentDueDate.Text        = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText).ToLongDateString();
                        txtAmountDue.Text             =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        dtpLatePaymentDueDate.Text    = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText).ToLongDateString();
                        txtLateAmountDue.Text         =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                    }
                }
            }

            XmlDocument xdCustomers = new XmlDocument();
            string? strCustomers = @"C:\Stellar Water Point6\Customers.xml";

            FileInfo? fiCustomers = new FileInfo(strCustomers);

            string strMeterNumber = string.Empty;

            if (fiCustomers.Exists)
            {
                using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdCustomers.Load(fsCustomers);
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + mtbAccountNumber.Text + "']")!;

                    foreach (XmlNode xnCustomer in xnlCustomers)
                    {
                        txtAccountName.Text = xnCustomer.NextSibling!.InnerText; // Account Name

                        strMeterNumber = xnCustomer.NextSibling.NextSibling!.InnerText;   // Meter Number
                        txtAccountType.Text = xnCustomer.NextSibling.NextSibling.NextSibling!.InnerText;   // Account Type
                        txtAddress.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // Address
                        txtCity.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // City
                        txtCounty.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;   // County
                        txtState.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;   // State
                        txtZIPCode.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText; // ZIP-Code
                    }
                }
            }

            XmlDocument xdWaterMeters = new XmlDocument();
            string? strWaterMeters = @"C:\Stellar Water Point6\WaterMeters.xml";

            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            if (fiWaterMeters.Exists)
            {
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterMeters.Load(fsWaterMeters);
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    // Check each node of the XML record
                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                    }
                }
            }
        }

        private void btnFindCustomerAccount_Click(object sender, EventArgs e)
        {
            XmlDocument xdCustomers = new XmlDocument();
            string? strCustomers = @"C:\Stellar Water Point6\Customers.xml";

            FileInfo? fiCustomers = new FileInfo(strCustomers);

            string strMeterNumber = string.Empty;

            if (fiCustomers.Exists)
            {
                using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdCustomers.Load(fsCustomers);
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + mtbAccountNumber.Text + "']")!;

                    foreach (XmlNode xnCustomer in xnlCustomers)
                    {
                        txtAccountName.Text = xnCustomer.NextSibling!.InnerText;
                        strMeterNumber = xnCustomer.NextSibling.NextSibling!.InnerText;
                        txtAccountType.Text = xnCustomer.NextSibling.NextSibling.NextSibling!.InnerText;
                        txtAddress.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;
                        txtCity.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;
                        txtCounty.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtState.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtZIPCode.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                    }
                }
            }

            XmlDocument xdWaterMeters = new XmlDocument();
            string? strWaterMeters = @"C:\Stellar Water Point6\WaterMeters.xml";

            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            if (fiWaterMeters.Exists)
            {
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterMeters.Load(fsWaterMeters);
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                    }
                }
            }
        }

        private void dtpMeterReadingEndDate_ValueChanged(object sender, EventArgs e)
        {
            TimeSpan tsDays = dtpMeterReadingEndDate.Value - dtpMeterReadingStartDate.Value;

            txtBillingDays.Text = (tsDays.Days + 1).ToString();
        }

        (double a, double b, double c) CalculateTiers(string acnt, double total)
        {
            (double tier1, double tier2, double tier3) results = (0.00, 0.00, 0.00);

            if (acnt == "RES")
            {
                results.tier1 = total * 41.50 / 10000.00;
                results.tier2 = total * 32.50 / 10000.00;
                results.tier3 = total * 26.00 / 10000.00;
            }
            else if (acnt == "SGO")
            {
                results.tier1 = total * 46 / 10000;
                results.tier2 = total * 50 / 10000;
                results.tier3 = total *  4 / 10000;
            }
            else if (acnt == "BUS")
            {
                results.tier1 = total * 45 / 10000;
                results.tier2 = total * 30 / 10000;
                results.tier3 = total * 25 / 10000;
            }
            else if (acnt == "UUO")
            {
                results.tier1 = total * 25 / 10000;
                results.tier2 = total * 35 / 10000;
                results.tier3 = total * 40 / 10000;
            }
            else if (acnt == "WAT")
            {
                results.tier1 = total * 50 / 10000;
                results.tier2 = total * 40 / 10000;
                results.tier3 = total * 10 / 10000;
            }
            else if (acnt == "OTH")
            {
                results.tier1 = total * (48.00 / 10000.00);
                results.tier2 = total * (32.00 / 10000.00);
                results.tier3 = total * (20.00 / 10000.00);
            }

            return results;
        }

        private double CalculateSewerCharges(string acnt, double total)
        {
            double result;

            if (acnt == "RES")
            {
                result = total * 6.826941 / 100;
            }
            else if (acnt == "SGO")
            {
                result = total * 4.162522 / 100;
            }
            else if (acnt == "BUS")
            {
                result = total * 8.3136 / 100;
            }
            else if (acnt == "UUO")
            {
                result = total * 10.6247 / 100;
            }
            else if (acnt == "WAT")
            {
                result = total * 12.0535 / 100;
            }
            else // OTH
            {
                result = total * 9.2065 / 100;
            }

            return result;
        }

        private double CalculateEnvironmentCharges(string acnt, double total)
        {
            double result;

            switch (acnt)
            {
                case "RES":
                    result = total * 0.022724;
                    break;
                case "SGO":
                    result = total * 0.118242;
                    break;
                case "BUS":
                    result = total * 0.161369;
                    break;
                case "UUO":
                    result = total * 0.082477;
                    break;
                case "WAT":
                    result = total * 0.413574;
                    break;
                default:
                    result = total * 0.22184;
                    break;
            }

            return result;
        }

        private double CalculateServiceCharges(string acnt, double total)
        {
            if (acnt == "RES")
            {
                return total * 0.145748;
            }
            else if (acnt == "SGO")
            {
                return total * 0.10224;
            }
            else if (acnt == "BUS")
            {
                return total * 0.242627;
            }
            else if (acnt == "UUO")
            {
                return total * 0.18669;
            }
            else if (acnt == "WAT")
            {
                return total * 0.412628;
            }
            else
            {
                return total * 0.210248;
            }
        }

        private double CalculateLocalTaxes(string acnt, double total) => acnt switch
        {
            "RES" => total * 0.031574,
            "SGO" => total * 0.035026,
            "BUS" => total * 0.122517,
            "UUO" => total * 0.105737,
            "WAT" => total * 0.153248,
            _ => total * 0.125148
        };

        private double CalculateStateTaxes(string acnt, double total) => acnt switch
        {
            "RES" => total * 0.016724,
            "SGO" => total * 0.008779,
            "BUS" => total * 0.042448,
            "UUO" => total * 0.067958,
            "WAT" => total * 0.081622,
            _ => total * 0.013746
        };

        private DateTime SetPaymentDueDate(string acnt, DateTime date)
        {
            TimeSpan tsPaymentDueDate = new TimeSpan(1, 0, 0, 0);

            if (acnt == "RES")
            {
                tsPaymentDueDate = new TimeSpan(15, 0, 0, 0);
            }
            else if (acnt == "SGO")
            {
                tsPaymentDueDate = new TimeSpan(20, 0, 0, 0);
            }
            else if (acnt == "BUS")
            {
                tsPaymentDueDate = new TimeSpan(30, 0, 0, 0);
            }
            else if (acnt == "UUO")
            {
                tsPaymentDueDate = new TimeSpan(15, 0, 0, 0);
            }
            else if (acnt == "WAT")
            {
                tsPaymentDueDate = new TimeSpan(40, 0, 0, 0);
            }
            else
            {
                tsPaymentDueDate = new TimeSpan(35, 0, 0, 0);
            }

            return date + tsPaymentDueDate;
        }

        private DateTime SetLatePaymentDueDate(string acnt, DateTime date)
        {
            TimeSpan tsLatePaymentDueDate = new TimeSpan(1, 0, 0, 0);

            if (acnt == "RES")
            {
                tsLatePaymentDueDate = new TimeSpan(30, 0, 0, 0);

                return date + tsLatePaymentDueDate;
            }
            else if (acnt == "SGO")
            {
                tsLatePaymentDueDate = new TimeSpan(40, 0, 0, 0);

                return date + tsLatePaymentDueDate;
            }
            else if (acnt == "BUS")
            {
                tsLatePaymentDueDate = new TimeSpan(50, 0, 0, 0);

                return date + tsLatePaymentDueDate;
            }
            else if (acnt == "UUO")
            {
                tsLatePaymentDueDate = new TimeSpan(60, 0, 0, 0);

                return date + tsLatePaymentDueDate;
            }
            else if (acnt == "WAT")
            {
                tsLatePaymentDueDate = new TimeSpan(65, 0, 0, 0);

                return date + tsLatePaymentDueDate;
            }
            else
            {
                tsLatePaymentDueDate = new TimeSpan(45, 0, 0, 0);

                return date + tsLatePaymentDueDate;
            }
        }

        private double CalculateLateAmountDue(string acnt, double amt)
        {
            double result;

            if (acnt == "RES")
            {
                result = amt + 8.95;
            }
            else if (acnt == "SGO")
            {
                result = amt + (amt / 4.575);
            }
            else if (acnt == "BUS")
            {
                result = amt + (amt / 12.315);
            }
            else if (acnt == "UUO")
            {
                result = amt + (amt / 7.425);
            }
            else if (acnt == "WAT")
            {
                result = amt + (amt / 15.225);
            }
            else
            {
                result = amt + (amt / 6.735);
            }

            return result;
        }

        private void btnEvaluateWaterBill_Click(object sender, EventArgs e)
        {
            double counterStart = 0, counterEnd = 0;

            try
            {
                counterStart = double.Parse(txtCounterReadingStart.Text);
            }
            catch (FormatException feCRStart)
            {
                MessageBox.Show("There was a problem with the value of the " +
                                "Counter Reading Start. The error produced is: " + feCRStart.Message,
                                "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }

            try
            {
                counterEnd = double.Parse(txtCounterReadingEnd.Text);
            }
            catch (FormatException feCREnd)
            {
                MessageBox.Show("There was a problem with the value of the " +
                                "Counter Reading End. The error produced is: " + feCREnd.Message,
                                "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }

            double consumption = counterEnd - counterStart;
            double gallons = consumption * 748.05;

            string strAccountType = txtAccountType.Text[..3];

            (double first, double second, double last) tiers = CalculateTiers(strAccountType, gallons);

            double waterCharges = tiers.first + tiers.second + tiers.last;
            double sewerCharges = CalculateSewerCharges(strAccountType, waterCharges);
            double envCharges = CalculateEnvironmentCharges(strAccountType, waterCharges);
            double srvCharges = CalculateServiceCharges(strAccountType, waterCharges);
            double totalCharges = waterCharges + sewerCharges + envCharges + srvCharges;
            double localTaxes = CalculateLocalTaxes(strAccountType, waterCharges);
            double stateTaxes = CalculateStateTaxes(strAccountType, waterCharges);
            double amtDue = totalCharges + localTaxes + stateTaxes;

            txtTotalHCF.Text = consumption.ToString();
            txtTotalGallons.Text = gallons.ToString("F");
            txtFirstTierConsumption.Text = tiers.first.ToString("F");
            txtSecondTierConsumption.Text = tiers.second.ToString("F");
            txtLastTierConsumption.Text = tiers.last.ToString("F");
            txtWaterCharges.Text = waterCharges.ToString("F");
            txtSewerCharges.Text = sewerCharges.ToString("F");
            txtEnvironmentCharges.Text = envCharges.ToString("F");
            txtServiceCharges.Text = srvCharges.ToString("F");
            txtTotalCharges.Text = totalCharges.ToString("F");
            txtLocalTaxes.Text = localTaxes.ToString("F");
            txtStateTaxes.Text = stateTaxes.ToString("F");
            dtpPaymentDueDate.Value = SetPaymentDueDate(strAccountType, dtpMeterReadingEndDate.Value);
            txtAmountDue.Text = amtDue.ToString("F");
            dtpLatePaymentDueDate.Value = SetLatePaymentDueDate(strAccountType, dtpMeterReadingEndDate.Value);
            txtLateAmountDue.Text = CalculateLateAmountDue(strAccountType, amtDue).ToString("F");
        }
    }
}

In the Solution Explorer, below the WaterBills folder, double-click Central.cs
From the Toolbox, add a button to the form below the list view and on the right side of the View Water Bill button

Change the characteristics of the button as follows:

Control	(Name)	Text	Other Properties
ListView	lvwWaterBills		No Change
Button	btnNewWaterBill		No Change
Button	btnViewWaterBill		No Change
Button	btnEditWaterBill	&Edit Water Bill...	Anchor: Bottom, Right

Double-click the Edit Water Bill button

Implement the event as follows:

using System.Xml;

namespace StellarWaterPoint3.WaterBills
{
    public partial class Central : Form
    {
        public Central()
        {
            InitializeComponent();
        }

        private void ShowWaterBills()
        {
            . . .
        }

        private void Central_Load(object sender, EventArgs e)
        {
            ShowWaterBills();
        }

        private void btnCreateWaterBill_Click(object sender, EventArgs e)
        {
            Create create = new();

            create.ShowDialog();

            ShowWaterBills();
        }

        private void btnViewWaterBill_Click(object sender, EventArgs e)
        {
            Details details = new();

            details.ShowDialog();
        }

        private void btnEditWaterBill_Click(object sender, EventArgs e)
        {
            Editor editor = new();

            if (editor.ShowDialog() == DialogResult.OK)
            {
                if (string.IsNullOrEmpty(editor.txtBillNumber.Text))
                {
                    MessageBox.Show("You must first type a bill number and then click the Find Water Bill button. " +
                                    "You can then optionally change some values on the water bill and save it.",
                                    "Stellar Water Point", MessageBoxButtons.OK);
                    return;
                }

                XmlDocument xdWaterBills = new XmlDocument();
                string? strWaterBills    = @"C:\Stellar Water Point6\WaterBills.xml";

                xdWaterBills.Load(strWaterBills);

                XmlNodeList xnlWaterBills = xdWaterBills.DocumentElement!.GetElementsByTagName("bill-number");

                foreach (XmlNode xnWaterBill in xnlWaterBills)
                {
                    if (xnWaterBill.InnerText.Contains(editor.txtBillNumber.Text))
                    {
                        xnWaterBill.ParentNode!.InnerXml =
                            "<bill-number>"              + editor.txtBillNumber.Text + "</bill-number>" +
                            "<account-number>"           + editor.mtbAccountNumber.Text + "</account-number>" +
                            "<meter-reading-start-date>" + editor.dtpMeterReadingStartDate.Value.ToShortDateString() + "</meter-reading-start-date>" +
                            "<meter-reading-end-date>"   + editor.dtpMeterReadingEndDate.Value.ToShortDateString() + "</meter-reading-end-date>" +
                            "<billing-days>"             + editor.txtBillingDays.Text + "</billing-days>" +
                            "<counter-reading-start>"    + editor.txtCounterReadingStart.Text + "</counter-reading-start>" +
                            "<counter-reading-end>"      + editor.txtCounterReadingEnd.Text + "</counter-reading-end>" +
                            "<total-hcf>"                + editor.txtTotalHCF.Text + "</total-hcf>" +
                            "<total-gallons>"            + editor.txtTotalGallons.Text + "</total-gallons>" +
                            "<first-tier-consumption>"   + editor.txtFirstTierConsumption.Text + "</first-tier-consumption>" +
                            "<second-tier-consumption>"  + editor.txtSecondTierConsumption.Text + "</second-tier-consumption>" +
                            "<last-tier-consumption>"    + editor.txtLastTierConsumption.Text + "</last-tier-consumption>" +
                            "<water-charges>"            + editor.txtWaterCharges.Text + "</water-charges>" +
                            "<sewer-charges>"            + editor.txtSewerCharges.Text + "</sewer-charges>" +
                            "<environment-charges>"      + editor.txtEnvironmentCharges.Text + "</environment-charges>" +
                            "<service-charges>"          + editor.txtEnvironmentCharges.Text + "</service-charges>" +
                            "<total-charges>"            + editor.txtTotalCharges.Text + "</total-charges>" +
                            "<state-taxes>"              + editor.txtStateTaxes.Text + "</state-taxes>" +
                            "<local-taxes>"              + editor.txtLocalTaxes.Text + "</local-taxes>" +
                            "<payment-due-date>"         + editor.dtpPaymentDueDate.Value.ToShortDateString() + "</payment-due-date>" +
                            "<amount-due>"               + editor.txtAmountDue.Text + "</amount-due>" +
                            "<late-payment-due-date>"    + editor.dtpLatePaymentDueDate.Value.ToShortDateString() + "</late-payment-due-date>" +
                            "<late-amount-due>"          + editor.txtLateAmountDue.Text + "</late-amount-due>";

                        xdWaterBills.Save(strWaterBills);
                        break;
                    }
                }
            }
            
            ShowWaterBills();
        }
    }
}

To execute the application, on the main menu, click Debug -> Start Without Debugging
On the main form of the application, click the Customers button:
Click the Edit Water Bill button:
In the Water Bill # text, type 923633
Click the Find Water Bill button

Change the following values:

Account #:                9249-379-6848 and click Find Customer Account
Meter Reading Start Date: 1/19/2010
Meter Reading End Date:   4/17/2010
Counter Reading Start:    256953
Counter Reading End:      256966

Click the Re-Evaluate Water Bill button:
Click the Update Water Bill button:
Close the forms and return to your programming environment

Deleting a Water Bill

Practical Learning: Deleting a Customer Account

To create a new form, in the Solution Explorer, right-click Water Bills -> New -> Form (Windows Forms)...
Set the name of the file and form to Delete
Click Add
Make that form the same size as the Water Bill - Details form
Select everything on the Water Bill - Details form and copy that selection
Paste that selection in the Water Bill - Delete form

Complete the design of the form as follows:

Control		(Name)	Text
Button		btnDeleteWaterBill	&Delete Water Bill

Using the Properties window, change some characteristics of the form as follows:

FormBorderStyle: FixedDialog
Text:            Stellar Water Point - Water Bill Deletion
StartPosition:   CenterScreen
MinimizeBox:     False
MaximizeBox:     False
ShowInTaskbar:   False

On the form, double-click the Find Water Bill button

Change the document as follows:

using System.Xml;

namespace StellarWaterPoint3.WaterBills
{
    public partial class Delete : Form
    {
        public Delete()
        {
            InitializeComponent();
        }

        private void btnFindWaterBill_Click(object sender, EventArgs e)
        {
            /* If the user clicks the Find Water Meter button, 
             * make sure there is an invoice number in the top text box. */
            if (string.IsNullOrEmpty(txtBillNumber.Text))
            {
                MessageBox.Show("You must provide a water bill number and then click the Find Water Bill button.",
                                "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
                // If the user didn't type a bill number but clicked Find Water Bill, don't do anything
                return;
            }

            XmlDocument xdWaterBills = new XmlDocument();
            string? strWaterBills = @"C:\Stellar Water Point6\WaterBills.xml";

            FileInfo? fiWaterBills = new FileInfo(strWaterBills);

            if (fiWaterBills.Exists)
            {
                using (FileStream? fsWaterBills = new FileStream(fiWaterBills.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterBills.Load(fsWaterBills);

                    /* Use XPath to locate the water bill that has 
                     * the same invoice number as the one in the Water Bill Number text box.
                     * Store the water bill in an XmlNodeList variable. */
                    XmlNodeList xnlWaterBills = xdWaterBills.DocumentElement!.SelectNodes("//bill-number[.='" + txtBillNumber.Text + "']")!;

                    foreach (XmlNode xnWaterBill in xnlWaterBills)
                    {
                        txtBillNumber.Text            =                xnWaterBill.FirstChild!.InnerText;
                        txtAccountNumber.Text         =                xnWaterBill.NextSibling!.InnerText;
                        txtMeterReadingStartDate.Text = DateTime.Parse(xnWaterBill.NextSibling.NextSibling!.InnerText).ToLongDateString();
                        txtMeterReadingEndDate.Text   = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling!.InnerText).ToLongDateString();
                        txtBillingDays.Text           =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;
                        txtCounterReadingStart.Text   =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText;
                        txtCounterReadingEnd.Text     =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtTotalHCF.Text              =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtTotalGallons.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtFirstTierConsumption.Text  =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtSecondTierConsumption.Text =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtLastTierConsumption.Text   =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtWaterCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtSewerCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtEnvironmentCharges.Text    =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtServiceCharges.Text        =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtTotalCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtStateTaxes.Text            =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtLocalTaxes.Text            =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtPaymentDueDate.Text        = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText).ToLongDateString();
                        txtAmountDue.Text             =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtLatePaymentDueDate.Text    = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText).ToLongDateString();
                        txtLateAmountDue.Text         =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                    }
                }
            }

            XmlDocument xdCustomers = new XmlDocument();
            // Declare a variable for a file that holds the list of customers
            string? strCustomers = @"C:\Stellar Water Point6\Customers.xml";

            // Create a FileInfo object for the customers
            FileInfo? fiCustomers = new FileInfo(strCustomers);

            // We will need to know the water meter associated with this customer account
            string strMeterNumber = string.Empty;

            // Check whether the file that holds a list of customers exists
            if (fiCustomers.Exists)
            {
                // If that exists, open it and pass it to a FileStream object
                using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    // Get the list of customers and pass the records to the XML DOM object created earlier
                    xdCustomers.Load(fsCustomers);
                    // Create an XmlNodeList list of customers using XPath
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + txtAccountNumber.Text + "']")!;

                    // Check each node of the XML record and display its values in each Windows control on the form
                    foreach (XmlNode xnCustomer in xnlCustomers)
                    {
                        //mtbAccountNumber.Text = xnCustomer.NextSibling!.InnerText;   // Meter #
                        txtAccountName.Text = xnCustomer.NextSibling!.InnerText; // Account Name

                        strMeterNumber = xnCustomer.NextSibling.NextSibling!.InnerText;   // Meter Number
                        txtAccountType.Text = xnCustomer.NextSibling.NextSibling.NextSibling!.InnerText;   // Account Type
                        txtAddress.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // Address
                        txtCity.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // City
                        txtCounty.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;   // County
                        txtState.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;   // State
                        txtZIPCode.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText; // ZIP-Code
                    }
                }
            }

            // Create an XML DOM object for the water meters records
            XmlDocument xdWaterMeters = new XmlDocument();
            // Declare a variable for a file that holds the list of water meters
            string? strWaterMeters = @"C:\Stellar Water Point6\WaterMeters.xml";

            // Create a FileInfo object for the customers
            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            // Check whether the file that holds a list of water meters exists
            if (fiWaterMeters.Exists)
            {
                // Get the list of water meters and pass the records to the XML DOM object
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    // Get the list of water meters and pass the records to the XML DOM object
                    xdWaterMeters.Load(fsWaterMeters);
                    // Create an XmlNodeList list of water meters using XPath
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    // Check each node of the XML record
                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        /* Get the values for the water meter.
                         * Create a sentence and display it in the Meter Details text box. */
                        txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                    }
                }
            }
        }
    }
}

Return to the Water Bills - Delete form and double-click the Delete Water Bill button
Return to the form and double-click the Close button

Change the document as follows:

using System.Xml;

namespace StellarWaterPoint3.WaterBills
{
    public partial class Delete : Form
    {
        public Delete()
        {
            InitializeComponent();
        }

        private void btnFindWaterBill_Click(object sender, EventArgs e)
        {
            /* If the user clicks the Find Water Meter button, 
             * make sure there is an invoice number in the top text box. */
            if (string.IsNullOrEmpty(txtBillNumber.Text))
            {
                MessageBox.Show("You must provide a water bill number and then click the Find Water Bill button.",
                                "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
                // If the user didn't type a bill number but clicked Find Water Bill, don't do anything
                return;
            }

            XmlDocument xdWaterBills = new XmlDocument();
            string? strWaterBills = @"C:\Stellar Water Point6\WaterBills.xml";

            FileInfo? fiWaterBills = new FileInfo(strWaterBills);

            if (fiWaterBills.Exists)
            {
                using (FileStream? fsWaterBills = new FileStream(fiWaterBills.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterBills.Load(fsWaterBills);

                    /* Use XPath to locate the water bill that has 
                     * the same invoice number as the one in the Water Bill Number text box.
                     * Store the water bill in an XmlNodeList variable. */
                    XmlNodeList xnlWaterBills = xdWaterBills.DocumentElement!.SelectNodes("//bill-number[.='" + txtBillNumber.Text + "']")!;

                    foreach (XmlNode xnWaterBill in xnlWaterBills)
                    {
                        txtBillNumber.Text            =                xnWaterBill.FirstChild!.InnerText;
                        txtAccountNumber.Text         =                xnWaterBill.NextSibling!.InnerText;
                        txtMeterReadingStartDate.Text = DateTime.Parse(xnWaterBill.NextSibling.NextSibling!.InnerText).ToLongDateString();
                        txtMeterReadingEndDate.Text   = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling!.InnerText).ToLongDateString();
                        txtBillingDays.Text           =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;
                        txtCounterReadingStart.Text   =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText;
                        txtCounterReadingEnd.Text     =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtTotalHCF.Text              =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtTotalGallons.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtFirstTierConsumption.Text  =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtSecondTierConsumption.Text =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtLastTierConsumption.Text   =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtWaterCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtSewerCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtEnvironmentCharges.Text    =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtServiceCharges.Text        =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtTotalCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtStateTaxes.Text            =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtLocalTaxes.Text            =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtPaymentDueDate.Text        = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText).ToLongDateString();
                        txtAmountDue.Text             =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                        txtLatePaymentDueDate.Text    = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText).ToLongDateString();
                        txtLateAmountDue.Text         =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                    }
                }
            }

            XmlDocument xdCustomers = new XmlDocument();
            // Declare a variable for a file that holds the list of customers
            string? strCustomers = @"C:\Stellar Water Point6\Customers.xml";

            // Create a FileInfo object for the customers
            FileInfo? fiCustomers = new FileInfo(strCustomers);

            // We will need to know the water meter associated with this customer account
            string strMeterNumber = string.Empty;

            // Check whether the file that holds a list of customers exists
            if (fiCustomers.Exists)
            {
                // If that exists, open it and pass it to a FileStream object
                using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    // Get the list of customers and pass the records to the XML DOM object created earlier
                    xdCustomers.Load(fsCustomers);
                    // Create an XmlNodeList list of customers using XPath
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + txtAccountNumber.Text + "']")!;

                    // Check each node of the XML record and display its values in each Windows control on the form
                    foreach (XmlNode xnCustomer in xnlCustomers)
                    {
                        //mtbAccountNumber.Text = xnCustomer.NextSibling!.InnerText;   // Meter #
                        txtAccountName.Text = xnCustomer.NextSibling!.InnerText; // Account Name

                        strMeterNumber = xnCustomer.NextSibling.NextSibling!.InnerText;   // Meter Number
                        txtAccountType.Text = xnCustomer.NextSibling.NextSibling.NextSibling!.InnerText;   // Account Type
                        txtAddress.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // Address
                        txtCity.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // City
                        txtCounty.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;   // County
                        txtState.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;   // State
                        txtZIPCode.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText; // ZIP-Code
                    }
                }
            }

            // Create an XML DOM object for the water meters records
            XmlDocument xdWaterMeters = new XmlDocument();
            // Declare a variable for a file that holds the list of water meters
            string? strWaterMeters = @"C:\Stellar Water Point6\WaterMeters.xml";

            // Create a FileInfo object for the customers
            FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);

            // Check whether the file that holds a list of water meters exists
            if (fiWaterMeters.Exists)
            {
                // Get the list of water meters and pass the records to the XML DOM object
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    // Get the list of water meters and pass the records to the XML DOM object
                    xdWaterMeters.Load(fsWaterMeters);
                    // Create an XmlNodeList list of water meters using XPath
                    XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    // Check each node of the XML record
                    foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                    {
                        /* Get the values for the water meter.
                         * Create a sentence and display it in the Meter Details text box. */
                        txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                    }
                }
            }
        }

        private void btnDeleteWaterBill_Click(object sender, EventArgs e)
        {
            XmlDocument xdWaterMeters = new XmlDocument();
            string? strWaterMeters = @"C:\Stellar Water Point6\WaterBills.xml";

            if (string.IsNullOrEmpty(txtBillNumber.Text))
            {
                MessageBox.Show("You must provide a bill number for the water bill you want to delete.",
                                "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
                return;
            }

            if (!File.Exists(strWaterMeters))
            {
                MessageBox.Show("There is no file for the water bills in the system.",
                                "Stellar Water Point",
                                MessageBoxButtons.OK, MessageBoxIcon.Information);
                return;
            }

            xdWaterMeters.Load(strWaterMeters);

            XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.GetElementsByTagName("bill-number");

            foreach (XmlNode xnWaterMeter in xnlWaterMeters)
            {
                if (xnWaterMeter.InnerText == txtBillNumber.Text)
                {
                    if (MessageBox.Show("Are you sure you want to delete this water bill from the system?",
                                        "Stellar Water Point",
                                        MessageBoxButtons.YesNo, MessageBoxIcon.Question) == DialogResult.Yes)
                    {
                        xdWaterMeters.DocumentElement.RemoveChild(xnWaterMeter.ParentNode!);
                        break;
                    }
                }
            }

            xdWaterMeters.Save(strWaterMeters);

            Close();
        }

        private void btnClose_Click(object sender, EventArgs e)
        {
            Close();
        }
    }
}

In the Solution Explorer, below the WaterBills folder, double-click Central.cs to open its form
From the Toolbox, add two buttons to the form below the list view and to the right of the Edit Water Bill button

Change the form design as follows:

Control	(Name)	Text	Other Properties
ListView	lvwWaterBills		Anchor: Bottom, Top, Bottom, Left, Right
Button	btnCreateWaterBill	&Create Water Bill...	Anchor: Bottom, Right
Button	btnViewWaterBill	&View Water Bill...	Anchor: Bottom, Right
Button	btnEditWaterBill	&Edit Water Bill...	Anchor: Bottom, Right
Button	btnDeleteWaterBill	&Delete Water Bill...	Anchor: Bottom, Right
Button	btnClose	&Close	Anchor: Bottom, Right

On the form, double-click the Delete Water Bill button
Return to the Water Bills - Central form and double-click the Close button

Implement the events as follows:

using System.Xml;

namespace StellarWaterPoint3.WaterBills
{
    public partial class Central : Form
    {
        public Central()
        {
            InitializeComponent();
        }

        private void ShowWaterBills()
        {
            lvwWaterBills.Items.Clear();

            XmlDocument xdWaterBills = new XmlDocument();
            string? strWaterBills = @"C:\Stellar Water Point6\WaterBills.xml";

            FileInfo? fiWaterBills = new FileInfo(strWaterBills);

            if (fiWaterBills.Exists)
            {
                using (FileStream? fsWaterBills = new FileStream(fiWaterBills.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterBills.Load(fsWaterBills);
                    XmlNodeList xnlWaterBills = xdWaterBills.DocumentElement!.ChildNodes;

                    int i = 1;

                    foreach (XmlNode xnWaterBill in xnlWaterBills)
                    {
                        ListViewItem lviWaterBill = new ListViewItem(i.ToString());

                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild!.InnerText);   // Water Bill #
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling!.InnerText);   // Account Number
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling!.InnerText); // Meter Reading Start Date
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling!.InnerText);   // Meter Reading End Date
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText); // Billing Days
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText);  // Counter Reading Start
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText);   // Counter Reading End
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText);   // Total HCF
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText);   // Gallons
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText);   // Payment Due Date
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText);  // Amount Due

                        lvwWaterBills.Items.Add(lviWaterBill);

                        i++;
                    }
                }
            }
        }

        private void Central_Load(object sender, EventArgs e)
        {
            ShowWaterBills();
        }

        private void btnCreateWaterBill_Click(object sender, EventArgs e)
        {
            Create create = new();

            create.ShowDialog();

            ShowWaterBills();
        }

        private void btnViewWaterBill_Click(object sender, EventArgs e)
        {
            Details details = new();

            details.ShowDialog();
        }

        private void btnEditWaterBill_Click(object sender, EventArgs e)
        {
            Editor editor = new();

            if (editor.ShowDialog() == DialogResult.OK)
            {
                if (string.IsNullOrEmpty(editor.txtBillNumber.Text))
                {
                    MessageBox.Show("You must first type a bill number and then click the Find Water Bill button. " +
                                    "You can then optionally change some values on the water bill and save it.",
                                    "Stellar Water Point", MessageBoxButtons.OK);
                    return;
                }

                // Create an XML DOM object
                XmlDocument xdWaterBills = new XmlDocument();
                // Prepare the path and name of the file that holds a list of water bills 
                string? strWaterBills = @"C:\Stellar Water Point6\WaterBills.xml";

                // Get the water bills records and store them in the above XML DOM object
                xdWaterBills.Load(strWaterBills);

                /* Create an XmlNodeList list that reprensents the XML elements from the list of water bills.
                 * Call the XML DOM's GetElementsByTagName() method. 
                 * To use the bill number elements as reference, pass the water bill number element as argument. */
                XmlNodeList xnlWaterBills = xdWaterBills.DocumentElement!.GetElementsByTagName("bill-number");

                // Visit each XML element of the list of water bills
                foreach (XmlNode xnWaterBill in xnlWaterBills)
                {
                    /* When you get to an element, find out if the value of its bill number is 
                     * the same as the bill number the user typed in the form. If that's the case, 
                     * change the value of each node of that element, using the values from the form. */
                    if (xnWaterBill.InnerText.Contains(editor.txtBillNumber.Text))
                    {
                        xnWaterBill.ParentNode!.InnerXml =
                            "<bill-number>"              + editor.txtBillNumber.Text            + "</bill-number>"                                   +
                            "<account-number>"           + editor.mtbAccountNumber.Text         + "</account-number>"                                +
                            "<meter-reading-start-date>" + editor.dtpMeterReadingStartDate.Value.ToShortDateString() + "</meter-reading-start-date>" +
                            "<meter-reading-end-date>"   + editor.dtpMeterReadingEndDate.Value.ToShortDateString()   + "</meter-reading-end-date>"   +
                            "<billing-days>"             + editor.txtBillingDays.Text           + "</billing-days>"                                  +
                            "<counter-reading-start>"    + editor.txtCounterReadingStart.Text   + "</counter-reading-start>"                         +
                            "<counter-reading-end>"      + editor.txtCounterReadingEnd.Text     + "</counter-reading-end>"                           +
                            "<total-hcf>"                + editor.txtTotalHCF.Text              + "</total-hcf>"                                     +
                            "<total-gallons>"            + editor.txtTotalGallons.Text          + "</total-gallons>"                                 +
                            "<first-tier-consumption>"   + editor.txtFirstTierConsumption.Text  + "</first-tier-consumption>"                        +
                            "<second-tier-consumption>"  + editor.txtSecondTierConsumption.Text + "</second-tier-consumption>"                       +
                            "<last-tier-consumption>"    + editor.txtLastTierConsumption.Text   + "</last-tier-consumption>"                         +
                            "<water-charges>"            + editor.txtWaterCharges.Text          + "</water-charges>"                                 +
                            "<sewer-charges>"            + editor.txtSewerCharges.Text          + "</sewer-charges>"                                 +
                            "<environment-charges>"      + editor.txtEnvironmentCharges.Text    + "</environment-charges>"                           +
                            "<service-charges>"          + editor.txtEnvironmentCharges.Text    + "</service-charges>"                               +
                            "<total-charges>"            + editor.txtTotalCharges.Text          + "</total-charges>"                                 +
                            "<state-taxes>"              + editor.txtStateTaxes.Text            + "</state-taxes>"                                   +
                            "<local-taxes>"              + editor.txtLocalTaxes.Text            + "</local-taxes>"                                   +
                            "<payment-due-date>"         + editor.dtpPaymentDueDate.Value.ToShortDateString() + "</payment-due-date>"                +
                            "<amount-due>"               + editor.txtAmountDue.Text             + "</amount-due>"                                    +
                            "<late-payment-due-date>"    + editor.dtpLatePaymentDueDate.Value.ToShortDateString() + "</late-payment-due-date>"       +
                            "<late-amount-due>"          + editor.txtLateAmountDue.Text         + "</late-amount-due>";

                        // After updating the elements, save the updated file
                        xdWaterBills.Save(strWaterBills);
                        // After saving the file, stop searching
                        break;
                    }
                }
            }

            /* Now that the user has closed the Water Bill - Editor dialog box (and probably 
             * updated the XML file for water bills), (re-)display the list of water bills.*/
            ShowWaterBills();
        }

        private void btnDeleteWaterBill_Click(object sender, EventArgs e)
        {
            Delete delete = new();

            delete.ShowDialog();

            ShowWaterBills();
        }

        private void btnClose_Click(object sender, EventArgs e)
        {
            Close();
        }
    }
}

To execute, on the main menu, click Debug -> Start Without Debugging:
On the Stellar Water Point form, click the Water Bills button
On the Water Bills form, click the Delete Water Bill button
In the Water Bill # text box, type 917829
Click Find Water Bill
Click Delete Water Bill
Read the message in the message box and click Yes:
Close the forms and return to your programming environment
From the Windows Explorer, open the WaterBills.xml file
Replace the content of the file with the provided file
Save the file
Return to your programming environment
Close Microsoft Visual Studio

Application


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