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The Nodes of an XML Element

 

An XML Node

 

Introduction to XML Nodes

Consider the following example of an XML file named Videos.xml:

<?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>
	<Video>
		<Title>Chalte Chalte</Title>
		<Director>Aziz Mirza</Director>
		<Length>145 Mins</Length>
		<Format>DVD</Format>
		<Rating>N/R</Rating>
	</Video>
</Videos>

An XML file appears as an upside-down tree: it has a root (in this case <Videos>), it can have branches (in this case <Video>), and it can have leaves (an example in this case is <Title>). As we have seen so far, all of these objects are created using the same technique: a tag with a name (such as <Title>) and an optional value. Based on their similarities, each of these objects is called a node. To support nodes of an XML file, the .NET Framework provides the XmlNode class, which is the ancestor to all types of nodes. XmlNode is an abstract class without a constructor. Based on this, to get a node, you must have an object that would produce one and you can only retrieve a node from an (existing) object.

Introduction to Node Types

To make XML as complete and as efficient as possible, it can contain various types of nodes. The categories or possible types of nodes are identified by an enumeration named XmlNodeType. If you use an XmlTextReader object to scan a file, when calling Read(), the class has a property named NodeType that allows you to identify the node that was read. NodeType is a read-only property of type XmlNodeType and it is declared as follows:

public override XmlNodeType NodeType { get; }

Therefore, when calling the XmlTextReader.Read() method, you can continuously check the value of the XmlTextReader.NodeType property to find out what type of node was just read, and then you can take an appropriate action.

 

Elements Fundamentals

 

Introduction

An element in an XML document is an object that begins with a start-tag, may contain a value, and may terminate with an end-tag. Based on this, the combination of a start-tag, the value, and the end-tag is called an element. An element can be more than that but for now, we will consider that an element is primarily characterized by a name and possibly a value.

To support XML elements, the System.Xml namespace provides the XmlElement class. XmlElement is based on a class named XmlLinkedNode that itself is based on XmlNode. To access an XML element, you can declare a variable of type XmlElement but the main purpose of this class is to get an element from a DOM object. For this reason, the XmlElement class doesn't have a constructor you can use. Instead, and as we will learn, the other classes have methods that produce an XmlElement element you can manipulate as necessary.

In the previous lesson, we saw that every XML file must have a root and we mentioned that you could call the XmlDocument.DocumentElement property to access it. This property is of type XmlElement and, to access it, you can declare an XmlElement variable and assign it this property. Here is an example:

using System;
using System.IO;
using System.Xml;

namespace VideoCollection1
{
    class Program
    {
        static int Main(string[] args)
        {
            string strFilename = "Videos.xml";
            XmlDocument xmlDoc = new XmlDocument();

            if (File.Exists(strFilename))
            {
                xmlDoc.Load(strFilename);
                XmlElement elm = xmlDoc.DocumentElement;
                Console.WriteLine("{0}", elm);
            }
            else
                Console.WriteLine("The file {0} could not be located",
                                  strFilename);

            Console.WriteLine();
            return 0;
        }
    }
}

This would produce:

System.Xml.XmlElement

Press any key to continue . . .

An XML element is represented in the XmlNodeType enumeration as the Element member. When using the Read() method of an XmlTextReader object, to find out if the item being read is an element, you can check whether the member of the current XmlNodeType is Element. Here is an example:

using System;
using System.IO;
using System.Xml;

namespace VideoCollection1
{
    class Program
    {
        static int Main(string[] args)
        {
            string strFilename = "Videos.xml";
            XmlDocument xmlDoc = new XmlDocument();

            if (File.Exists(strFilename))
            {
                XmlTextReader rdrXml = new XmlTextReader(strFilename);

                do {
                    switch (rdrXml.NodeType)
                    {
                        case XmlNodeType.Element:
                            break;
                    }
                }while (rdrXml.Read());
            }
            else
                Console.WriteLine("The file {0} could not be located",
                                  strFilename);

            Console.WriteLine();
            return 0;
        }
    }
}

Practical Learning Practical Learning: Introducing XML Elements

  1. Start Microsoft Visual C# and create a Console Application named CollegeParkAutoParts2
  2. On the main menu, click Project -> Add New Item...
  3. In the Templates list, click XML File
  4. Set the Name to makes and click Add
  5. Change the file as follows:
     
    <?xml version="1.0" encoding="utf-8"?>
    <Makes>
      <Make>Acura</Make>
      <Make>Audi</Make>
      <Make>BMW</Make>
      <Make>Chevrolet</Make>
    </Makes>
  6. On the main menu, click File -> Save makes.xml As...
  7. Access the main folder of the current project and, inside of it, open a sub-folder of the same name (it should be opened already). In the sub-folder of the same name, open the bin sub-folder followed by the Release sub-folder
     
  8. Click Save

The Name of an Element

The name of an element is the string that represents the tag. For example, in <Director>, the word Director is the name of the element. An element must have at least a start-tag. All of the tags we have seen so far were created as elements. When creating your elements, remember to follow the rules we defined for names.

The XmlElement class is equipped with the Name property that can be used to identify an existing element. Here is an example of accessing it:

using System;
using System.IO;
using System.Xml;

namespace VideoCollection1
{
    class Program
    {
        static int Main(string[] args)
        {
            string strFilename = "Videos.xml";
            XmlDocument xmlDoc = new XmlDocument();

            if (File.Exists(strFilename))
            {
                xmlDoc.Load(strFilename);
                XmlElement elm = xmlDoc.DocumentElement;
                Console.WriteLine("{0}", elm.Name);
            }
            else
                Console.WriteLine("The file {0} could not be located",
                                  strFilename);

            Console.WriteLine();
            return 0;
        }
    }
}

This would produce:

Videos

Press any key to continue . . .

Notice that Videos is returned as the name of the root element of the file. If calling the Read() method of an XmlTextReader object to scan a file, when you get to an element, you can find out its Name identity by accessing it. Here is an example:

using System;
using System.IO;
using System.Xml;

namespace VideoCollection1
{
    class Program
    {
        static int Main(string[] args)
        {
            string strFilename = "Videos.xml";
            XmlDocument xmlDoc = new XmlDocument();

            if (File.Exists(strFilename))
            {
                XmlTextReader rdrXml = new XmlTextReader(strFilename);

                do {
                    switch (rdrXml.NodeType)
                    {
                        case XmlNodeType.Element:
                            Console.WriteLine("{0}", rdrXml.Name);
                            break;
                    }
                }while (rdrXml.Read());
            }
            else
                Console.WriteLine("The file {0} could not be located",
                                  strFilename);

            Console.WriteLine();
            return 0;
        }
    }
}

This would produce:

Videos
Video
Title
Director
Length
Format
Rating
Video
Title
Director
Length
Format
Rating
Video
Title
Director
Length
Format
Rating

Press any key to continue . . .

The Text or Value of an Element

The value of an element is the item displayed on the right side of the start-tag. It is also called the text of the element. In the case of <Director>Jonathan Lynn</Director>, the "Jonathan Lynn" string is the value of the Director element. To support the text or value of an element, the XmlElement class is equipped with the Value property.

While the value of one element can be a number, the value of another element can be a date. Yet another element can use a regular string as its value. Consider the following example:

<?xml version="1.0" encoding="utf-8" ?>
<Employees>
	<Employee>
		<FullName>Lydia Thomason</FullName>
		<Salary>25.64</Salary>
		<DepartmentID>1</DepartmentID>
	</Employee>
	<Employee>
		<FullName>June Grath</FullName>
		<Salary>16.38</Salary>
		<DepartmentID>4</DepartmentID>
	</Employee>
</Employees>

Notice that the Salary elements contain numbers that look like currency values and the DepartmentID elements use an integer as value.

If you are using an XmlTextReader object to scan a file, when the Read() method gets to an element, you can find out what its value is by accessing this property. Here is an example:

using System;
using System.IO;
using System.Xml;

namespace VideoCollection1
{
    class Program
    {
        static int Main(string[] args)
        {
            string strFilename = "Videos.xml";
            XmlDocument xmlDoc = new XmlDocument();

            if (File.Exists(strFilename))
            {
                XmlTextReader rdrXml = new XmlTextReader(strFilename);

                do {
                    switch (rdrXml.NodeType)
                    {
                        case XmlNodeType.Text:
                            Console.WriteLine("{0}", rdrXml.Value);
                            break;
                    }
                }while (rdrXml.Read());
            }
            else
                Console.WriteLine("The file {0} could not be located",
                                  strFilename);

            Console.WriteLine();
            return 0;
        }
    }
}

This would produce:

The Distinguished Gentleman
Jonathan Lynn
112 Minutes
DVD
R
Her Alibi
Bruce Beresford
94 Mins
DVD
PG-13
Chalte Chalte
Aziz Mirza
145 Mins
DVD
N/R

Press any key to continue . . .

The value or text of an element is an object of type XmlText.

 

Practical Learning Practical Learning: Getting the Text of an Element

  1. Access the Program.cs file and change it as follows::
     
    using System;
    using System.IO;
    using System.Xml;
    
    namespace CollegeParkAutoParts2
    {
        class Program
        {
            static int Main(string[] args)
            {
                FileStream fsCPAP = null;
                string strFilename = "makes.xml";
                XmlDocument xmlDoc = new XmlDocument();
    
                if (File.Exists(strFilename))
                {
                    fsCPAP = new FileStream(strFilename,
                                            FileMode.Open,
                                            FileAccess.Read);
                    XmlTextReader rdrXml = new XmlTextReader(fsCPAP);
    
                    do
                    {
                        switch (rdrXml.NodeType)
                        {
                            case XmlNodeType.Text:
                                Console.WriteLine("Make: {0}",
                                                  rdrXml.Value);
                                break;
                        }
                    } while (rdrXml.Read());
                }
                else
                    Console.WriteLine("The {0} file was not found",
                                      strFilename);
    
                Console.WriteLine();
                return 0;
            }
        }
    }
  2. Execute the application to see the result. This would produce:
     
    Make: Acura
    Make: Audi
    Make: BMW
    Make: Chevrolet
    
    Press any key to continue . . .
  3. Close the DOS window

Empty Elements

An element may not have a value but only a name. Consider the following example:

<?xml version="1.0" encoding="utf-8"?>
<Videos>
  <Video>
    <Title>The Distinguished Gentleman</Title>
    <Director>Jonathan Lynn</Director>
  </Video>
</Videos>

In this case, the Video element doesn't have a value. It is called an empty element. When a tag is empty, the Value property of its XmlElement object would return an empty value. Consider the following code:

using System;
using System.IO;
using System.Xml;

namespace VideoCollection1
{
    class Program
    {
        static int Main(string[] args)
        {
            string strFilename = "Videos.xml";
            XmlDocument xmlDoc = new XmlDocument();

            if (File.Exists(strFilename))
            {
                xmlDoc.Load(strFilename);
                XmlElement elm = xmlDoc.DocumentElement;
                Console.WriteLine("{0}", elm.Value);
            }
            else
                Console.WriteLine("The file {0} could not be located",
                                  strFilename);

            Console.WriteLine();
            return 0;
        }
    }
}

This would produce:

Press any key to continue . . .

Because the Videos node doesn't have its own value, its Value property returns an empty string.

Character Entities in an Element Value

Besides these obvious types of values, you may want to display special characters as values of elements. Consider the following example:

<?xml version="1.0" encoding="utf-8" ?>
<Employees>
	<Employee>
		<FullName>Sylvie <Bellie> Aronson</FullName>
		<Salary>25.64</Salary>
		<DepartmentID>1</DepartmentID>
	</Employee>
	<Employee>
		<FullName>Bertrand Yamaguchi</FullName>
		<Salary>16.38</Salary>
		<DepartmentID>4</DepartmentID>
	</Employee>
</Employees>

If you try using this XML document, for example, if you try displaying it in a browser, you would, receive an error:

An XML file in a browser

The reason is that when the parser reaches the <FullName>Sylvie <Bellie> Aronson</FullName> line, it thinks that <Bellie> is a tag but then <Bellie> is not closed. The parser concludes that the document is not well-formed, that there is an error. For this reason, to display a special symbol as part of a value, you can use its character code. For example, the < (less than) character is represented with &lt and the > (greater than) symbol can be used with &gt;. Therefore, the above code can be corrected as follows:

<?xml version="1.0" encoding="utf-8" ?>
<Employees>
	<Employee>
		<FullName>Sylvie &lt;Bellie&gt; Aronson</FullName>
		<Salary>25.64</Salary>
		<DepartmentID>1</DepartmentID>
	</Employee>
	<Employee>
		<FullName>Bertrand Yamaguchi</FullName>
		<Salary>16.38</Salary>
		<DepartmentID>4</DepartmentID>
	</Employee>
</Employees>

This would produce:

Here is a list of other codes you can use for special characters:

Code Symbol Code Symbol Code Symbol Code Symbol Code Symbol
&apos; ' &#067; C &#106; j &#179; &#218;
&lt; < &#068; D &#107; k &#180; &#219;
&gt; > &#069; E &#108; l &#181; &#220;
&amp; & &#070; F &#109; m &#182; &#221;
&quot; " &#071; G &#110; n &#183; &#222;
&#033; ! &#072; H &#111; o &#184; &#223;
&#034; " &#073; I &#112; p &#185; &#224;
&#035; # &#074; J &#113; q &#186; &#225;
&#036; $ &#075; K &#114; r &#187; &#226;
&#037; % &#076; L &#115; s &#188; &#227;
&#038; & &#077; M &#116; t &#189; &#228;
&#039; ' &#078; N &#117; u &#190; &#229;
&#040; ( &#079; O &#118; v &#191; &#230;
&#041; ) &#080; P &#119; w &#192; &#231;
&#042; * &#081; Q &#120; x &#193; &#232;
&#043; + &#082; R &#121; y &#194; &#233;
&#044; , &#083; S &#122; z &#195; &#234;
&#045; - &#084; T &#123; { &#196; &#235;
&#046; . &#085; U &#125; } &#197; &#236;
&#047; / &#086; V &#126; ~ &#198; &#237;
&#048; 0 &#087; W &#160; empty &#199; &#238;
&#049; 1 &#088; X &#161; &#200; &#239;
&#050; 2 &#089; Y &#162; &#201; &#240;
&#051; 3 &#090; Z &#163; &#202; &#241;
&#052; 4 &#091; [ &#164; &#203; &#242;
&#053; 5 &#092; \ &#165; &#204; &#243;
&#054; 6 &#093; ] &#166; &#205; &#244;
&#055; 7 &#094; ^ &#167; &#206; &#245;
&#056; 8 &#095; _ &#168; &#207; &#246;
&#057; 9 &#096; ` &#169; &#208; &#247;
&#058; : &#097; a &#170; &#209; &#248;
&#059; ; &#098; b &#171; &#210; &#249;
&#060; < &#099; c &#172; &#211; &#250;
&#061; = &#100; d &#173; &#212; &#251;
&#062; > &#101; e &#174; &#213; &#252;
&#063; ? &#102; f &#175; &#214; &#253;
&#064; @ &#103; g &#176; &#215; &#254;
&#065; A &#104; h &#177; &#216; &#255;
&#066; B &#105; i &#178; &#217; &#256; A

There are still other codes to include special characters in an XML file.

 

Practical Learning Practical Learning: Introducing XML Elements

  1. In the Solution Explorer, right-click CollegeParkAutoParts2 -> Add -> New Item...
  2. In the Templates list, make sure XML File is selected.
    Set the Name to models and click Add
  3. To save the file, on the main menu, click File -> Save models.xml As...
  4. Access the main folder of the current project and, inside of it, open a sub-folder of the same name (it should be selected already). In the sub-folder of the same name, open the bin sub-folder followed by the Release sub-folder. Click Save
  5. Change the file as follows:
     
    <?xml version="1.0" encoding="utf-8" ?>
    <Models>
    	<Model>NSX</Model>
    	<Model>TL</Model>
    	<Model>Spider</Model>
    	<Model>A4</Model>
    	<Model>RS6</Model>
    	<Model>323I</Model>
    	<Model>M5</Model>
    	<Model>Astro</Model>
    	<Model>Cavalier</Model>
    	<Model>Prot&#233;g&#233;</Model>
    </Models>
  6. Access the Program.cs file and modify it as follows:
     
    using System;
    using System.IO;
    using System.Xml;
    
    namespace CollegeParkAutoParts2
    {
        class Program
        {
            static int Main(string[] args)
            {
                FileStream fsCPAP = null;
                string strFilename = "models.xml";
                XmlDocument xmlDoc = new XmlDocument();
    
                if (File.Exists(strFilename))
                {
                    fsCPAP = new FileStream(strFilename,
                                            FileMode.Open,
                                            FileAccess.Read);
                    XmlTextReader rdrXml = new XmlTextReader(fsCPAP);
    
                    do
                    {
                        switch (rdrXml.NodeType)
                        {
                            case XmlNodeType.Text:
                                Console.WriteLine("Model: {0}",
                                                  rdrXml.Value);
                                break;
                        }
                    } while (rdrXml.Read());
                }
                else
                    Console.WriteLine("The {0} file was not found",
                                      strFilename);
    
                Console.WriteLine();
                return 0;
            }
        }
    }
  7. Execute the application to see the result:
     
    Model: NSX
    Model: TL
    Model: Spider
    Model: A4
    Model: RS6
    Model: 323I
    Model: M5
    Model: Astro
    Model: Cavalier
    Model: Protg
    
    Press any key to continue . . .
  8. Close the DOS window

Identifying the Markup of a Node

 

The Inner Text of a node

In the previous sections, we have seen how to create a tag to produce a node. We also saw that a node could be placed inside of another node. The combined text of the values of the children of a node is available through its XmlNode.InnerText property which is declared as follows:

public virtual string InnerText{get; set};

This property concatenates the values of the children of the node that called them and doesn't include their markups. Here is an example:

using System;
using System.IO;
using System.Xml;

namespace VideoCollection1
{
    class Program
    {
        static int Main(string[] args)
        {
            string strFilename = "Videos.xml";
            XmlDocument xmlDoc = new XmlDocument();

            if (File.Exists(strFilename))
            {
                xmlDoc.Load(strFilename);
                XmlElement elm = xmlDoc.DocumentElement;
                Console.WriteLine("{0}", elm.InnerText);
            }
            else
                Console.WriteLine("The file {0} could not be located",
                                  strFilename);

            Console.WriteLine();
            return 0;
        }
    }
}

This would produce:

The Distinguished GentlemanJonathan Lynn112 MinutesDVDRHer AlibiBruce Beresford9
4 MinsDVDPG-13Chalte ChalteAziz Mirza145 MinsDVDN/R

Press any key to continue . . .

Notice that this property produces all values of the children of a node in one block. We already saw how to access each value of the children of a node by calling the XmlTextReader.Read() method and get its Text.

The Outer XML Code of a node

If you want to get a node, its markup, its child(ren) and its(their) markup(s), you can access its XmlNode.OuterXml property which is declared as follows:

public virtual string OuterXml{get};

Here is an example:

using System;
using System.IO;
using System.Xml;

namespace VideoCollection1
{
    class Program
    {
        static int Main(string[] args)
        {
            string strFilename = "Videos.xml";
            XmlDocument xmlDoc = new XmlDocument();

            if (File.Exists(strFilename))
            {
                xmlDoc.Load(strFilename);
                XmlElement elm = xmlDoc.DocumentElement;
                Console.WriteLine("{0}", elm.OuterXml);
            }
            else
                Console.WriteLine("The file {0} could not be located",
                                  strFilename);

            Console.WriteLine();
            return 0;
        }
    }
}

This would produce:

<Videos><Video><Title>The Distinguished Gentleman</Title><Director>Jonathan Lynn
</Director><Length>112 Minutes</Length><Format>DVD</Format><Rating>R</Rating></V
ideo><Video><Title>Her Alibi</Title><Director>Bruce Beresford</Director><Length>
94 Mins</Length><Format>DVD</Format><Rating>PG-13</Rating></Video><Video><Title>
Chalte Chalte</Title><Director>Aziz Mirza</Director><Length>145 Mins</Length><Fo
rmat>DVD</Format><Rating>N/R</Rating></Video></Videos>

Press any key to continue . . .

The Inner XML Code of a node

If you want only the markup(s) of the child(ren) excluding the parent, access its XmlNode.InnerXml property which is declared as follows:

public virtual string InnerXml{get};

Here is an example:

Console.WriteLine("{0}", elm.InnerXml);

This would produce:

<Video><Title>The Distinguished Gentleman</Title><Director>Jonathan Lynn</Direct
or><Length>112 Minutes</Length><Format>DVD</Format><Rating>R</Rating></Video><Vi
deo><Title>Her Alibi</Title><Director>Bruce Beresford</Director><Length>94 Mins<
/Length><Format>DVD</Format><Rating>PG-13</Rating></Video><Video><Title>Chalte C
halte</Title><Director>Aziz Mirza</Director><Length>145 Mins</Length><Format>DVD
</Format><Rating>N/R</Rating></Video>

Press any key to continue . . .

The  Child Nodes of  a Node

 

Introduction

As mentioned already, one node can be nested inside of another. A nested node is called a child of the nesting node. This also implies that a node can have as many children as necessary, making them child nodes of the parent node. In our Videos.xml example, the Title and the Director nodes are children of the Video node. The Video node is the parent of both the Title and the Director nodes.

A Collection of Child Nodes

To support the child nodes of a particular node, the XmlNode class is equipped with the ChildNodes property. To identify the collection of child nodes of a node, the .NET Framework provides the XmlNodeList class. Therefore, the ChildNodes property of an XmlNode object is of type XmlNodeList. This property is declared as follows:

public virtual XmlNodeList ChildNodes{get};

When this property is used, it produces an XmlNodeList list, which is a collection of all nodes that share the same parent. Each item in the collection is of type XmlNode. To give you the number of nodes on an XmlNodeList collection, the class is equipped with a property named Count. Here is an example of using it:

using System;
using System.IO;
using System.Xml;

namespace VideoCollection
{
    class Program
    {
        static int Main(string[] args)
        {
            string strFilename = "Videos.xml";
            XmlDocument xmlDoc = new XmlDocument();

            if (File.Exists(strFilename))
            {
                xmlDoc.Load(strFilename);
                XmlElement elm = xmlDoc.DocumentElement;
                XmlNodeList lstVideos = elm.ChildNodes;

                Console.WriteLine("The root element contains {0} nodes",
                                  lstVideos.Count);
            }
            else
                Console.WriteLine("The file {0} could not be located",
                                  strFilename);

            Console.WriteLine();
            return 0;
        }
    }
}

This would produce:

The root element contains 3 nodes

Press any key to continue . . .

You can also use the Count property in a for loop to visit the members of the collection.

Accessing a Node in a Collection

The children of a node, that is, the members of a ChildNodes property, or the members of an XmlNodeList collection, can be located each by an index. The first node has an index of 0, the second has an index of 1, an so on. To give you access to a node of the collection, the XmlNodeList class is equipped with an indexed property and a method named Item. Both produce the same result. For example, if a node has three children, to access the third, you can apply an index of 2 to its indexed property. Here is an example:

using System;
using System.IO;
using System.Xml;

namespace VideoCollection
{
    class Program
    {
        static int Main(string[] args)
        {
            string strFilename = "Videos.xml";
            XmlDocument xmlDoc = new XmlDocument();

            if (File.Exists(strFilename))
            {
                xmlDoc.Load(strFilename);
                XmlElement elm = xmlDoc.DocumentElement;
                XmlNodeList lstVideos = elm.ChildNodes;

                Console.WriteLine(lstVideos[2]);;
 
            }
            else
                Console.WriteLine("The file {0} could not be located",
                                  strFilename);

            Console.WriteLine();
            return 0;
        }
    }
}

You can also use the Item() method to get the same result. Using a for loop, you can access each node and display the values of its children as follows:

using System;
using System.IO;
using System.Xml;

namespace VideoCollection
{
    class Program
    {
        static int Main(string[] args)
        {
            string strFilename = "Videos.xml";
            XmlDocument xmlDoc = new XmlDocument();

            if (File.Exists(strFilename))
            {
                xmlDoc.Load(strFilename);
                XmlElement elm = xmlDoc.DocumentElement;
                XmlNodeList lstVideos = elm.ChildNodes;

                for (int i = 0; i < lstVideos.Count; i++)
                    Console.WriteLine("{0}",lstVideos[i].InnerText );
            }
            else
                Console.WriteLine("The file {0} could not be located",
                                  strFilename);

            Console.WriteLine();
            return 0;
        }
    }
}

This would produce:

The Distinguished GentlemanJonathan Lynn112 MinutesDVDR
Her AlibiBruce Beresford94 MinsDVDPG-13
Chalte ChalteAziz Mirza145 MinsDVDN/R

Press any key to continue . . .

Instead of using the indexed property, the XmlNodeList class implements the IEnumerable interface. This allows you to use a foreach loop to visit each node of the collection. Here is an example:

using System;
using System.IO;
using System.Xml;

namespace VideoCollection
{
    class Program
    {
        static int Main(string[] args)
        {
            string strFilename = "Videos.xml";
            XmlDocument xmlDoc = new XmlDocument();

            if (File.Exists(strFilename))
            {
                xmlDoc.Load(strFilename);
                XmlElement elm = xmlDoc.DocumentElement;
                XmlNodeList lstVideos = elm.ChildNodes;

                foreach(XmlNode node in lstVideos)
                    Console.WriteLine("{0}", node);
            }
            else
                Console.WriteLine("The file {0} could not be located",
                                  strFilename);

            Console.WriteLine();
            return 0;
        }
    }
}

This would produce:

System.Xml.XmlElement
System.Xml.XmlElement
System.Xml.XmlElement

Press any key to continue . . .

To better manage and manipulate the nodes of a collection of nodes, you must be able to access the desired node. The XmlNode combined with the XmlNodeList classes provide various means of getting to a node and taking the appropriate actions.

The Parent of a Node

Not all nodes have children, obviously. For example, the Title node of our Videos.xml file doesn't have children. To find out whether a node has children, check its HasChildNodes Boolean property that is declared as follows:

public virtual bool HasChildNodes{get};

If a node is a child, to get its parent, you can access its ParentNode property.

The First Child Node

The children of a nesting node are also recognized by their sequence. For our Videos.xml file, the first line is called the first child of the DOM. This would be:

<?xml version="1.0" encoding="utf-8"?>

After identifying or locating a node, the first node that immediately follows it is referred to as its first child. In our Videos.xml file, the first child of the first Video node is the <Title>The Distinguished Gentleman</Title> element. The first child of the second Video> node is <Title>Her Alibi</Title>.

In the .NET Framework, the first child of a node can be retrieved by accessing the XmlNode.FirstChild property declared as follows:

public virtual XmlNode FirstChild{get};

In the following example, every time the parser gets to a Video node, it displays the value of it first child:

using System;
using System.IO;
using System.Xml;

namespace VideoCollection
{
    class Program
    {
        static int Main(string[] args)
        {
            string strFilename = "Videos.xml";
            XmlDocument xmlDoc = new XmlDocument();

            if (File.Exists(strFilename))
            {
                xmlDoc.Load(strFilename);
                XmlElement elm = xmlDoc.DocumentElement;
                XmlNodeList lstVideos = elm.ChildNodes;

                for (int i = 0; i < lstVideos.Count; i++)
                    Console.WriteLine("{0}",
                        lstVideos[i].FirstChild.InnerText );
            }
            else
                Console.WriteLine("The file {0} could not be located",
                                  strFilename);

            Console.WriteLine();
            return 0;
        }
    }
}

This would produce:

The Distinguished Gentleman
Her Alibi
Chalte Chalte

Press any key to continue . . .

In this example, we started our parsing on the root node of the document. At times, you will need to consider only a particular node, such as the first child of a node. For example, you may want to use only the first child of the root. To get it, you can access the FirstChild property of the DocumentElement object of the DOM. Once you get that node, you can then do what you judge necessary. In the following example, only the values of the child nodes of the first child of the root are displayed:

using System;
using System.IO;
using System.Xml;

namespace VideoCollection
{
    class Program
    {
        static int Main(string[] args)
        {
            string strFilename = "Videos.xml";
            XmlDocument xmlDoc = new XmlDocument();

            if (File.Exists(strFilename))
            {
                xmlDoc.Load(strFilename);
                XmlNode node = xmlDoc.DocumentElement.FirstChild;
                XmlNodeList lstVideos = node.ChildNodes;

                for (int i = 0; i < lstVideos.Count; i++)
                    Console.WriteLine("{0}",
                        lstVideos[i].InnerText );
            }
            else
                Console.WriteLine("The file {0} could not be located",
                                  strFilename);

            Console.WriteLine();
            return 0;
        }
    }
}

This would produce:

The Distinguished Gentleman
Jonathan Lynn
112 Minutes
DVD
R

Press any key to continue . . .

Consider the following modification of the Videos.xml file:

<?xml version="1.0" encoding="utf-8" ?>
<Videos>
	<Video>
		<Title>The Distinguished Gentleman</Title>
		<Director>Jonathan Lynn</Director>
		<CastMembers>
			<Actor>Eddie Murphy</Actor>
			<Actor>Lane Smith</Actor>
			<Actor>Sheryl Lee Ralph</Actor>
			<Actor>Joe Don Baker</Actor>
			<Actor>Victoria Rowell</Actor>
		</CastMembers>
		<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>
	<Video>
		<Title>Chalte Chalte</Title>
		<Director>Aziz Mirza</Director>
		<Length>145 Mins</Length>
		<Format>DVD</Format>
		<Rating>N/R</Rating>
	</Video>
</Videos>

Remember that when using a for or a foreach loop applied to an XmlNodeList collection, each node that you access is a complete XmlNode object and may have children. This means that you can further get the ChildNodes node of any node. Here is an example that primarily scans the nodes but looks for one whose name is CastMembers:

using System;
using System.IO;
using System.Xml;

namespace VideoCollection
{
    class Program
    {
        static int Main(string[] args)
        {
            string strFilename = "Videos.xml";
            XmlDocument xmlDoc = new XmlDocument();

            if (File.Exists(strFilename))
            {
                xmlDoc.Load(strFilename);
                // Locate the root node and 
                // get a reference to its first child
                XmlNode node = xmlDoc.DocumentElement.FirstChild;
                // Create a list of the child nodes of 
                // the first node under the root
                XmlNodeList lstVideos = node.ChildNodes;

                // Visit each node
                for (int i = 0; i < lstVideos.Count; i++)
                {
                    // Look for a node named CastMembers
                    if (lstVideos[i].Name == "CastMembers")
                    {
                        // Once/if you find it,
                        // 1. Access its first child
                        // 2. Create a list of its child nodes
                        XmlNodeList lstActors =
                            lstVideos[i].ChildNodes;
                        // Display the values of the nodes
                        for (int j = 0; j < lstActors.Count; j++)
                            Console.WriteLine("{0}",
                                lstActors[j].InnerText);
                    }
                }
            }
            else
                Console.WriteLine("The file {0} could not be located",
                                  strFilename);

            Console.WriteLine();
            return 0;
        }
    }
}

This would produce:

Eddie Murphy
Lane Smith
Sheryl Lee Ralph
Joe Don Baker
Victoria Rowell

Press any key to continue . . .

As we have learned that a node or a group of nodes can be nested inside of another node. When you get to a node, you may know or find out that it has children. You may then want to consider only the first child. Here is an example:

using System;
using System.IO;
using System.Xml;

namespace VideoCollection
{
    class Program
    {
        static int Main(string[] args)
        {
            string strFilename = "Videos.xml";
            XmlDocument xmlDoc = new XmlDocument();

            if (File.Exists(strFilename))
            {
                xmlDoc.Load(strFilename);
                // Locate the root node and 
                // get a reference to its first child
                XmlNode node = xmlDoc.DocumentElement.FirstChild;
                // Create a list of the child nodes of 
                // the first node under the root
                XmlNodeList lstVideos = node.ChildNodes;

                // Visit each node
                for (int i = 0; i < lstVideos.Count; i++)
                {
                    // Look for a node named CastMembers
                    if (lstVideos[i].Name == "CastMembers")
                    {
                        // Once/if you find it,
                        // 1. Access its first child
                        // 2. Create a list of its child nodes
                        XmlNodeList lstActors =
                            lstVideos[i].FirstChild.ChildNodes;
                        // Display the value of its first child node
                        for (int j = 0; j < lstActors.Count; j++)
                            Console.WriteLine("{0}",
                                lstActors[j].InnerText);
                    }
                }
            }
            else
                Console.WriteLine("The file {0} could not be located",
                                  strFilename);

            Console.WriteLine();
            return 0;
        }
    }
}

This would produce:

Eddie Murphy

Press any key to continue . . .

The Last Child Node

As opposed to the first child, the child node that immediately precedes the end-tag of the parent node is called the last child. To get the last child of a node, you can access its XmlNode.LastChild property that is declared as follows:

public virtual XmlNode LastChild{get};

The Siblings of a Node

The child nodes that are nested in a parent node and share the same level are referred to as siblings. Consider the above file: Director, CastMembers, and Length are child nodes of the Video node but the Actor node is not a child of the Video node. Consequently, Director, Actors, and Length are siblings.

Obviously, to get a sibling, you must first have a node. To access the sibling of a node, you can use its XmlNode.NextSibling property, which is declared as follows:

public virtual XmlNode NextSibling{get};

 

 

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