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Operations on XML Elements

 

Adding a Simple Element

To programmatically create a new element, you can declare an XmlElement variable. To add the new element to the file, the XmlDocument class provides the CreateElement() method that is overloaded with three versions. One of the versions uses the following syntax:

public XmlElement CreateElement(string name);

Using this method, to create a new element, call it and pass it the name of the new element. If you want the element to have a value, the XmlDocument class is equipped with the CreateTextNode() method. This method returns an XmlText value. The syntax of this method is:

public virtual XmlText CreateTextNode(string text);

This method takes as argument the string that would constitute the value of the element. The calls to XmlDocument.CreateElement() and XmlDocument.CreateTextNode() allow you to initialize a new element. In order to actually add the new element, you must specify its position in the tree: whether it would be the first or the last node, whether you want to position it before or after a node of your choice. To support the positions of existing nodes, the XmlNode class, which is the ancestor of all XML nodes of the .NET Framework, provides various appropriate methods.

 One of these methods is AppendChild(), which is used to add an element as the last child of its parent. The syntax of the XmlNode.AppendChild() method is:

public virtual XmlNode AppendChild(XmlNode newChild);

Imagine you have a simple XML file that has only the root and one level of elements as follows:

<?xml version="1.0" encoding="utf-8"?>
<Holidays>
  <Holiday>New Year's Day</Holiday>
  <Holiday>Birthday of Martin Luther King, Jr.</Holiday>
  <Holiday>Washington's Birthday</Holiday>
</Holidays>

To add a new Holiday element to this file, based on the above discussions, you can use code as follows:

void AddHoliday()
{
	XmlDocument docXML = new XmlDocument();
	docXML.Load("Holidays.xml");

	XmlElement elmXML = docXML.CreateElement("Holiday");
	XmlText    txtXML = docXML.CreateTextNode("Memorial Day");
	docXML.DocumentElement.AppendChild(elmXML);
	docXML.DocumentElement.LastChild.AppendChild(txtXML);

	docXML.Save("Holidays.xml");
}

Practical Learning Practical Learning: Adding Elements

  1. To give the user the ability to create a new car make, change the Exercise.cs file as follows:
     
    // Project Name: CPAP1
    // Application:  College Park Auto-Parts
    // Purpose:      To Process XML Files
    
    using System;
    using System.Xml;
    
    namespace CPAP1
    {
        static void CreateNewMake()
        {
    	string strNewMake = 0;
    
    	Console.Write("Enter Car Make: ")
    	strNewMake = Console.ReadLine();
    
    	// Open the Makes.xml file
    	XmlDocument docXMLFile = new XmlDocument();
    	docXMLFile.Load("Makes.xml");
    
    	// Get the root node so we can explore its children
    	XmlElement nodRoot     = docXMLFile.DocumentElement;
    	// Store all the values of the elements in a string
    	string allMyChildren   = nodRoot.InnerText;
    	// Locate the new make among the values of the elements
    	int indexLookForNewMake = allMyChildren.IndexOf(strNewMake);
    					 
    	// If the car make exists already, don't add it
    	if( indexLookForNewMake >= 0 )
    	    return;
    	else
    	{
    	    // If the car is not in the list already, add it as a Make element
    	    XmlElement elmXML = docXMLFile.CreateElement("Make");
    	    // Create its value using the string provided by the user
    	    XmlText    txtXML = docXMLFile.CreateTextNode(strNewMake);
    	    // Add the new element at the end of the file
    	    docXMLFile.DocumentElement.AppendChild(elmXML);
    	    // Specify its text
    	    docXMLFile.DocumentElement.LastChild.AppendChild(txtXML);
    
    	    // Save the file
    	    docXMLFile.Save("Makes.xml");
    	}
        }
    
        class Exercise
        {
            static int Main()
            {
    	    return 0;
            }
        }
    }
  2. To give the user the ability to add a new car model, create the following function in the file:
     
    // Project Name: CPAP1
    // Application:  College Park Auto-Parts
    // Purpose:      To Process XML Files
    
    using System;
    using System.Xml;
    
    namespace CPAP1
    {
        static void CreateNewMake()
        {
    	string strNewMake = 0;
    
    	Console.Write("Enter Car Make: ")
    	strNewMake = Console.ReadLine();
    
    	// Open the Makes.xml file
    	XmlDocument docXMLFile = new XmlDocument();
    	docXMLFile.Load("Makes.xml");
    
    	// Get the root node so we can explore its children
    	XmlElement nodRoot     = docXMLFile.DocumentElement;
    	// Store all the values of the elements in a string
    	string allMyChildren   = nodRoot.InnerText;
    	// Locate the new make among the values of the elements
    	int indexLookForNewMake = allMyChildren.IndexOf(strNewMake);
    					 
    	// If the car make exists already, don't add it
    	if( indexLookForNewMake >= 0 )
    	    return;
    	else
    	{
    	    // If the car is not in the list already, add it as a Make element
    	    XmlElement elmXML = docXMLFile.CreateElement("Make");
    	    // Create its value using the string provided by the user
    	    XmlText    txtXML = docXMLFile.CreateTextNode(strNewMake);
    	    // Add the new element at the end of the file
    	    docXMLFile.DocumentElement.AppendChild(elmXML);
    	    // Specify its text
    	    docXMLFile.DocumentElement.LastChild.AppendChild(txtXML);
    
    	    // Save the file
    	    docXMLFile.Save("Makes.xml");
    	}
        }
    
        static void CreateNewModel()
        {
    	string strNewModel = 0;
    
    	Console.Write("Enter Car Model: ")
    	strNewModel = Console.ReadLine();
    
    	XmlDocument docXMLFile = new XmlDocument();
    	docXMLFile.Load("Models.xml");
    
    	XmlElement nodRoot   = docXMLFile.DocumentElement;
    	string allMyChildren = nodRoot.InnerText;
    	int indexNewModel    = allMyChildren.IndexOf(strNewModel);
    					 
    	if( indexNewModel >= 0 )
    	    return;
    	else
    	{
    	    XmlElement elmXML = docXMLFile.CreateElement("Model");
    	    XmlText    txtXML = docXMLFile.CreateTextNode(strNewModel);
    	  
    	    docXMLFile.DocumentElement.AppendChild(elmXML);
    	    docXMLFile.DocumentElement.LastChild.AppendChild(txtXML);
    
    	    docXMLFile.Save("Models.xml");
    	}
        }
    
        class Exercise
        {
            static int Main()
            {
    	    return 0;
            }
        }
    }
  3. To guide the user with a menu, change the file as follows:
     
    // Project Name: CPAP1
    // Application:  College Park Auto-Parts
    // Purpose:      To Process XML Files
    
    using System;
    using System.Xml;
    
    namespace CPAP1
    {
        class Exercise
        {
    	static void CreateNewMake()
    	{
    	    string strNewMake = null;
    
    	    Console.Write("Enter Car Make: ");
    	    strNewMake = Console.ReadLine();
    
    	    // Open the Makes.xml file
    	    XmlDocument docXMLFile = new XmlDocument();
    	    docXMLFile.Load("Makes.xml");
    
    	    // Get the root node so we can explore its children
    	    XmlElement nodRoot     = docXMLFile.DocumentElement;
    	    // Store all the values of the elements in a string
    	    string allMyChildren   = nodRoot.InnerText;
    	    // Locate the new make among the values of the elements
    	    int indexLookForNewMake = allMyChildren.IndexOf(strNewMake);
     
    	    // If the car make exists already, don't add it
    	    if( indexLookForNewMake >= 0 )
    		return;
    	    else
    	    {
    		// If the car is not in the list already, add it as a Make element
    		XmlElement elmXML = docXMLFile.CreateElement("Make");
    		// Create its value using the string provided by the user
    		XmlText    txtXML = docXMLFile.CreateTextNode(strNewMake);
    		// Add the new element at the end of the file
    		docXMLFile.DocumentElement.AppendChild(elmXML);
    		// Specify its text
    		docXMLFile.DocumentElement.LastChild.AppendChild(txtXML);
    
    		// Save the file
    		docXMLFile.Save("Makes.xml");
    	    }
    	}
    
    	static void CreateNewModel()
    	{
    	    string strNewModel = null;
    
    	    Console.Write("Enter Car Model: ");
    	    strNewModel = Console.ReadLine();
    
    	    XmlDocument docXMLFile = new XmlDocument();
    	    docXMLFile.Load("Models.xml");
    
    	    XmlElement nodRoot   = docXMLFile.DocumentElement;
    	    string allMyChildren = nodRoot.InnerText;
    	    int indexNewModel    = allMyChildren.IndexOf(strNewModel);
    			 
    	    if( indexNewModel >= 0 )
    		return;
    	    else
    	    {
    		XmlElement elmXML = docXMLFile.CreateElement("Model");
    		XmlText    txtXML = docXMLFile.CreateTextNode(strNewModel);
    
    		docXMLFile.DocumentElement.AppendChild(elmXML);
    		docXMLFile.DocumentElement.LastChild.AppendChild(txtXML);
    
    		docXMLFile.Save("Models.xml");
    	    }
    	}
    
            static int Main()
            {
    	    char mnuChoice = 'q';
    
    	    Console.WriteLine();
    	    Console.WriteLine("=o=o=o=o=o=o=o=o=o=o=o=o=o=o=o=");
    	    Console.WriteLine("=-= College Park Auto-Parts =-=");
    	    Console.WriteLine("=o=o=o=o=o=o=o=o=o=o=o=o=o=o=o=");
    	    
    	    do {
    		Console.WriteLine("=-= Main Menu =-=");
    		Console.WriteLine("0 - Exit");
    		Console.WriteLine("1 - Add New Car Make");
    		Console.WriteLine("2 - Add New Car Model");
    		Console.Write("Your Choice: ");
    		mnuChoice = char.Parse(Console.ReadLine());
    
    		if( mnuChoice == '1' )
    		    CreateNewMake();
    		else if( mnuChoice == '2' )
    		    CreateNewModel();
    
    		if ( (mnuChoice != '0') && (mnuChoice != '1') && (mnuChoice != '2') )
    		    Console.WriteLine("Invalid Choice: Please try again");
    	    } while( mnuChoice != '0' );
    
    
    	    Console.WriteLine("Thank you!");
    	    return 0;
            }
        }
    }
  4. Save the file
  5. Open  the Command Prompt and Change to the Directory that contains the above file, CPAP1
  6. To compile the exercise, type csc Exercise.cs and press Enter
  7. To execute the application, type Exercise and press Enter
  8. Using the menu, try adding a few car manufacturers (like Toyota and Honda) and a few makes (like Neon, Civic, Camry, and Spider) 
  9. Return to Notepad

Adding a Filled Child Element

The above Holidays.xml file had only one level under the root and no child element of the root had children. Suppose you have a file as follows:

<?xml version="1.0" encoding="utf-8"?>
<Videos>
  <Video>
    <Title>The Distinguished Gentleman</Title>
    <Director>Jonathan Lynn</Director>
    <Length>112 Minutes</Length>
    <Format>DVD</Format>
    <Rating>R</Rating>
  </Video>
  <Video>
    <Title>Her Alibi</Title>
    <Director>Bruce Beresford</Director>
    <Length>94 Mins</Length>
    <Format>DVD</Format>
    <Rating>PG-13</Rating>
  </Video>
</Videos>

Imagine that you want to add a Video element. You have a choice of adding one, more, or all child elements of the Video node. To perform this operation, one solution you can use is to "build" all child elements of the Video element, then add the node as a whole. To support this technique, we saw earlier that the XmlNode.InnerXml property comprises a node, its markup, its children and their markup. This means that you can create the child nodes with their markup(s) as a string and assign that string to an XmlNode.InnerXml string. To do this, you would need the set version of the InnerXml property. It is declared as follows:

public virtual string InnerXml{get; set;}

Here is an example that adds a complete new Video node to the above XML file:

static void DoIt()
{
	 XmlDocument docXML = new XmlDocument();
	 docXML.Load("Videos.xml");

	 XmlElement elmXML = docXML.CreateElement("Video");
	 string strNewVideo = "<Title>Other People's Money</Title>" +
		                      "<Director>Alan Brunstein</Director>" +
			      "<Length>114 Minutes</Length>" +
			      "<Format>VHS</Format>" +
			      "<Rating>PG-13</Rating>";

	 elmXML.InnerXml = strNewVideo;
	 docXML.DocumentElement.AppendChild(elmXML);

	 docXML.Save("Videos.xml");
}

If you have an XML file with different levels and you want to add an element as a new child to a particular element, you can first locate that element. One way you can do this is to call the XmlDocument.GetElementByTagName() method. This method is overloaded with two versions. One of its versions has the following syntax:

public virtual XmlNodeList GetElementsByTagName(string name);

This method takes as argument the name of the element that you want to locate. If the method finds that element, it returns a list of all child nodes of that element as an XmlNodeList object. This XmlNodeList object represents a collection of nodes where each node can be located by its index through the ItemOf indexed property.

Practical Learning Practical Learning: Adding Elements

  1. To allow the user to create new parts, change the source code as follows:
     
    // Project Name: CPAP1
    // Application:  College Park Auto-Parts
    // Purpose:      To Process XML Files
    
    using System;
    using System.Xml;
    
    namespace CPAP1
    {
        class Exercise
        {
    	static void CreateNewMake()
    	{
    	    string strNewMake = null;
    
    	    Console.Write("Enter Car Make: ");
    	    strNewMake = Console.ReadLine();
    
    	    // Open the Makes.xml file
    	    XmlDocument docXMLFile = new XmlDocument();
    	    docXMLFile.Load("Makes.xml");
    
    	    // Get the root node so we can explore its children
    	    XmlElement nodRoot     = docXMLFile.DocumentElement;
    	    // Store all the values of the elements in a string
    	    string allMyChildren   = nodRoot.InnerText;
    	    // Locate the new make among the values of the elements
    	    int indexLookForNewMake = allMyChildren.IndexOf(strNewMake);
     
    	    // If the car make exists already, don't add it
    	    if( indexLookForNewMake >= 0 )
    		return;
    	    else
    	    {
    		// If the car is not in the list already, add it as a Make element
    		XmlElement elmXML = docXMLFile.CreateElement("Make");
    		// Create its value using the string provided by the user
    		XmlText    txtXML = docXMLFile.CreateTextNode(strNewMake);
    		// Add the new element at the end of the file
    		docXMLFile.DocumentElement.AppendChild(elmXML);
    		// Specify its text
    		docXMLFile.DocumentElement.LastChild.AppendChild(txtXML);
    
    		// Save the file
    		docXMLFile.Save("Makes.xml");
    	    }
    	}
    
    	static void CreateNewModel()
    	{
    	    string strNewModel = null;
    
    	    Console.Write("Enter Car Model: ");
    	    strNewModel = Console.ReadLine();
    
    	    XmlDocument docXMLFile = new XmlDocument();
    	    docXMLFile.Load("Models.xml");
    
    	    XmlElement nodRoot   = docXMLFile.DocumentElement;
    	    string allMyChildren = nodRoot.InnerText;
    	    int indexNewModel    = allMyChildren.IndexOf(strNewModel);
    			 
    	    if( indexNewModel >= 0 )
    		return;
    	    else
    	    {
    		XmlElement elmXML = docXMLFile.CreateElement("Model");
    		XmlText    txtXML = docXMLFile.CreateTextNode(strNewModel);
    
    		docXMLFile.DocumentElement.AppendChild(elmXML);
    		docXMLFile.DocumentElement.LastChild.AppendChild(txtXML);
    
    		docXMLFile.Save("Models.xml");
    	    }
    	}
    
    	static void AddNewPart()
    	{
    	    int carYear;
    	    string strMake, strModel, strPartNumber, strPartName;
    	    double unitPrice;
    
    	    //// - Generate a random number between 100000 and 999999 - ////
    
    	    // We will generate a random number for the item
    	    // To start, we will use the miliseconds as a seed
    	    int ms = DateTime.Now.Millisecond;
    	    Random rndNumber = new Random(ms);
    	    int next = rndNumber.Next(100000, 999999);
    	    // Display the new number in the Part # text box
    	    strPartNumber = next.ToString();
    
    	    //// - Let the user specify the car model year - ////
    	    int curYear = DateTime.Now.Year + 1;
    
    	    Console.WriteLine("Enter the following information as is related to the new car part");
    	    Console.WriteLine("For the car model that the new part is made for, enter the year");
    	    Console.Write("between 1960 and " + curYear + ": ");
    	    carYear = int.Parse(Console.ReadLine());
    
    	    //// - Display the list of Makes to the user to select one - ////
    	    // We will need a reference to the XML document
    	    XmlDocument docXML = new XmlDocument();
    
    	    // Open the Makes.xml file
    	    docXML.Load("Makes.xml");
    
    	    // Get a reference to the root node
    	    XmlElement nodRoot = docXML.DocumentElement;
    	    // Locate all nodes whose name is Make
    	    XmlNodeList nodItems = nodRoot.GetElementsByTagName("Make");
    	    // Retrieve the value of each Make node and display
    	    // that value to the user
    	    Console.WriteLine("Here is a list of the car makes in our system");
    	    for(int i = 0; i < nodItems.Count; i++)
    		Console.WriteLine(nodItems[i].InnerXml);
    	    Console.Write("From this list, enter the car make of the new part: ");
    	    strMake = Console.ReadLine();
    	    Console.WriteLine("=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=");
    
    	    //// - Display the list of car Models to the user to select one - ////
    	    // Open the Models.xml file
    	    docXML.Load("Models.xml");
    
    	    // Get a reference to the root node
    	    nodRoot = docXML.DocumentElement;
    	    // Locate all nodes whose name is Model
    	    nodItems = nodRoot.GetElementsByTagName("Model");
    	    // Retrieve the value of each Model node and display
    	    // that value to the user
    	    Console.WriteLine("Here is a list of the car models in our system");
    	    for(int i = 0; i < nodItems.Count; i++)
    		Console.WriteLine(nodItems[i].InnerXml);
    	    Console.Write("From this list, enter the car model of the part: ");
    	    strModel = Console.ReadLine();
    	    Console.WriteLine("=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=");
    
    	    //// - Request the part name - ////
    	    Console.Write("Enter Part Name:  ");
    	    strPartName = Console.ReadLine();
    
    	    //// - Request the unit price - ////
    	    Console.Write("Enter Unit Price: ");
    	    unitPrice = double.Parse(Console.ReadLine());
    
    	    Console.WriteLine("=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=");
    	    Console.WriteLine("New Car Part Summary");
    	    Console.WriteLine("=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=");
    	    Console.WriteLine("Part #:     " + strPartNumber);
    	    Console.WriteLine("Model Year: " + carYear);
    	    Console.WriteLine("Car Make:   " + strMake);
    	    Console.WriteLine("Car Model:  " + strModel);
    	    Console.WriteLine("Part Name:  " + strPartName);
    	    Console.WriteLine("Unit Price: " + unitPrice);
    	    Console.WriteLine("=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=");
    
    	    // XmlDocument docXML = new XmlDocument();
    	    docXML.Load("Parts.xml");
    
    	    XmlElement elmXML = docXML.CreateElement("Part");
    	    string strNewPart = "<PartNumber>" + strPartNumber + "</PartNumber>" +
    	                        "<CarYear>" + carYear.ToString() + "</CarYear>" +
    	                        "<Make>" + strMake + "</Make>" +
    			        "<Model>" + strModel + "</Model>" +
    			        "<PartName>" + strPartName + "</PartName>" +
    			        "<UnitPrice>" + unitPrice.ToString() + "</UnitPrice>";
    
    	    elmXML.InnerXml = strNewPart;
    	    docXML.DocumentElement.AppendChild(elmXML);
    
    	    docXML.Save("Parts.xml");
    	}
    
            static int Main()
            {
    	    char mnuChoice = 'q';
    
    	    Console.WriteLine();
    	    Console.WriteLine("=o=o=o=o=o=o=o=o=o=o=o=o=o=o=o=");
    	    Console.WriteLine("=-= College Park Auto-Parts =-=");
    	    Console.WriteLine("=o=o=o=o=o=o=o=o=o=o=o=o=o=o=o=");
    	    
    	    do {
    		Console.WriteLine("=-= Main Menu =-=");
    		Console.WriteLine("0 - Exit");
    		Console.WriteLine("1 - Add New Car Make");
    		Console.WriteLine("2 - Add New Car Model");
    		Console.WriteLine("3 - Add New Car Part");
    		Console.Write("Your Choice: ");
    		mnuChoice = char.Parse(Console.ReadLine());
    
    		if( mnuChoice == '1' )
    		    CreateNewMake();
    		else if( mnuChoice == '2' )
    		    CreateNewModel();
    		else if( mnuChoice == '3' )
    		    AddNewPart();
    
    		if ( (mnuChoice != '0') && (mnuChoice != '1') &&
    		     (mnuChoice != '2') && (mnuChoice != '3') )
    		    Console.WriteLine("Invalid Choice: Please try again\n");
    	    } while( mnuChoice != '0' );
    
    
    	    Console.WriteLine("Thank you!");
    	    return 0;
            }
        }
    }
  2. Save the file and return to the Command Prompt
  3. To compile the exercise, type csc Exercise.cs and press Enter
  4. To execute the application, type Exercise and press Enter
  5. Using the menu, try adding a few car parts. Here are examples:
     
    =o=o=o=o=o=o=o=o=o=o=o=o=o=o=o=
    =-= College Park Auto-Parts =-=
    =o=o=o=o=o=o=o=o=o=o=o=o=o=o=o=
    =-= Main Menu =-=
    0 - Exit
    1 - Add New Car Make
    2 - Add New Car Model
    3 - Add New Car Part
    Your Choice: 3
    Enter the following information as is related to the new car part
    For the car model that the new part is made for, enter the year
    between 1960 and 2006: 1996
    Here is a list of the car makes in our system
    Acura
    BMW
    Dodge
    Toyota
    Honda
    Hyundai
    From this list, enter the car make of the new part: Dodge
    =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
    Here is a list of the car models in our system
    NSX
    TL
    Spider
    A4
    RS6
    323I
    M5
    Neon
    Civic
    Camry
    From this list, enter the car model of the part: Neon
    =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
    Enter Part Name:  Brake Pads
    Enter Unit Price: 34.95
    =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
    New Car Part Summary
    =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
    Part #:     973417
    Model Year: 1996
    Car Make:   Dodge
    Car Model:  Neon
    Part Name:  Brake Pads
    Unit Price: 34.95
    =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
    =-= Main Menu =-=
    0 - Exit
    1 - Add New Car Make
    2 - Add New Car Model
    3 - Add New Car Part
    Your Choice: 3
    Enter the following information as is related to the new car part
    For the car model that the new part is made for, enter the year
    between 1960 and 2006: 1996
    Here is a list of the car makes in our system
    Acura
    BMW
    Dodge
    Toyota
    Honda
    Hyundai
    From this list, enter the car make of the new part: Honda
    =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
    Here is a list of the car models in our system
    NSX
    TL
    Spider
    A4
    RS6
    323I
    M5
    Neon
    Civic
    Camry
    From this list, enter the car model of the part: Civic
    =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
    Enter Part Name:  Passenger Mirror
    Enter Unit Price: 24.65
    =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
    New Car Part Summary
    =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
    Part #:     719266
    Model Year: 1996
    Car Make:   Honda
    Car Model:  Civic
    Part Name:  Passenger Mirror
    Unit Price: 24.65
    =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
    =-= Main Menu =-=
    0 - Exit
    1 - Add New Car Make
    2 - Add New Car Model
    3 - Add New Car Part
    Your Choice: 3
    Enter the following information as is related to the new car part
    For the car model that the new part is made for, enter the year
    between 1960 and 2006: 1998
    Here is a list of the car makes in our system
    Acura
    BMW
    Dodge
    Toyota
    Honda
    Hyundai
    From this list, enter the car make of the new part: Honda
    =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
    Here is a list of the car models in our system
    NSX
    TL
    Spider
    A4
    RS6
    323I
    M5
    Neon
    Civic
    Camry
    From this list, enter the car model of the part: Civic
    =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
    Enter Part Name:  Brake Pads
    Enter Unit Price: 34.85
    =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
    New Car Part Summary
    =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
    Part #:     879207
    Model Year: 1998
    Car Make:   Honda
    Car Model:  Civic
    Part Name:  Brake Pads
    Unit Price: 34.85
    =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
    =-= Main Menu =-=
    0 - Exit
    1 - Add New Car Make
    2 - Add New Car Model
    3 - Add New Car Part
    Your Choice: 0
    Thank you!
    
    C:\CSharp Lessons\CPAP1>
  6. Type Exit and press Enter to close the DOS window
  7. Close Notepad to end the lesson

Element Navigation

An XML tree navigation consists of visiting the various nodes of the file, for any necessary reason. One reason would be that you want to insert a new element at a specific position in the tree. Another would be that you want to check whether a certain node is already present in the tree.

As always, there are various ways you can perform an operation such as navigating a tree. To "scan" a file from top to bottom, thus visiting each type of node in the XML file, you can use the XmlTextReader class. This class is equipped with all types of properties and methods you would need.

If you want to navigate to a specific node in the tree, you can use the XmlDocument.GetElementByTagName() method that we used previously.

 
 

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