C# XML: Operations on XML Elements

	Inserting an Element

Locating an Element

So far, we have been adding nodes quite randomly, that is, without much precision. In some cases, you may want to perform an operation on an existing and particular node. For example, you may want to change the value of a node, you may want to add a new child node to an existing node, etc. Before taking any of these actions, you must be able to locate or identify the desired element.

To assist you with finding a node, the XmlDocument class is equipped with the GetElementByTagName() method which is overloaded with two versions. One of the syntaxes used is:

public virtual XmlNodeList GetElementsByTagName(string name);

This method takes as argument a string. The string must be the Name of a node. If at least one node that holds that name exists in the file, this method returns a collection of the nodes with that name. If there is no node with that name, the collection is returned empty and there is no exception.

Here is an example of calling the method:

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);

                // Get a reference to the root node
                XmlElement elmRoot = xmlDoc.DocumentElement;

                // Create a list of nodes whose name is Title
                XmlNodeList lstTitles = xmlDoc.GetElementsByTagName("Title");

                // Now you can check each node of the list
                foreach(XmlNode node in lstTitles)
                {
                    ;
                }
            }

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

Once you have a list of the nodes of a particular criterion, you can then act as you see fit. For example, For example, you can look for a particular node that holds a text of your choice. 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);

                // Get a reference to the root node
                XmlElement elmRoot = xmlDoc.DocumentElement;
                //XmlNodeList lstVideos = xmlDoc.GetElementsByTagName("Video");

                // Create a list of nodes whose name is Title
                XmlNodeList lstTitles = xmlDoc.GetElementsByTagName("Title");

                // Now you can check each node of the list
                foreach(XmlNode node in lstTitles)
                {
                    if (node.InnerText == "Her Alibi")
                    {
                        ;
                    }
                }
            }

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

Insertion an Element as a Last Child

Once again, consider our Videos.xml file:

<?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>The Day After Tomorrow</Title>
    <Director>Roland Emmerich</Director>
    <Length>124 Minutes</Length>
    <Format>DVD</Format>
    <Rating>PG-13</Rating>
  </Video>
</Videos>

Imagine you want to add a list of actors of the Her Alibi video. The first action to take is to locate the video, which you can do by calling the XmlDocument.GetElementsByTagName() method applied to a collection of nodes whose names are Video. From this list of nodes, you can look for the node whose value is "Her Alibi". Once you have found this element, get a reference to its parent. Then add the new node as the LastChild object of its parent. This can be done as follows:

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);

                // Get a reference to the root node
                XmlElement elmRoot = xmlDoc.DocumentElement;

                // Create a list of nodes whose name is Title
                XmlNodeList lstTitles = xmlDoc.GetElementsByTagName("Title");

                // visit each node named Title
                foreach(XmlNode node in lstTitles)
                {
                    // When you get to a node, look for the element's value
                    // If you find an element whose value is Her Alibi
                    if (node.InnerText == "Her Alibi")
                    {
                        // Create an element named Actors
                        XmlElement elmNew = xmlDoc.CreateElement("Actors");
                        XmlNode elmParent = node.ParentNode;
                        // Add a new element named Actors to it
                        elmParent.AppendChild(elmNew);
                        xmlDoc.Save(strFilename);
                    }
                }
            }

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

This would produce:

<?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>
    <Actors />
  </Video>
  <Video>
    <Title>The Day After Tomorrow</Title>
    <Director>Roland Emmerich</Director>
    <Length>124 Minutes</Length>
    <Format>DVD</Format>
    <Rating>PG-13</Rating>
  </Video>
</Videos>

This code creates an empty element. If you want to create an element that includes a value, create its text and add that text as the LastChild of its parent. 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);

                // Get a reference to the root node
                XmlElement elmRoot = xmlDoc.DocumentElement;

                // Create a list of nodes whose name is Title
                XmlNodeList lstTitles = xmlDoc.GetElementsByTagName("Title");

                // visit each node named Title
                foreach(XmlNode node in lstTitles)
                {
                    // When you get to a node, look for the element's value
                    // If you find an element whose value is Her Alibi
                    if (node.InnerText == "The Distinguished Gentleman")
                    {
                        // Create an element named Category
                        XmlElement elmNew = xmlDoc.CreateElement("Category");
                        // Create the text of the new element
                        XmlText txtCatetory = xmlDoc.CreateTextNode("Comedy");
                    // Get a reference to the parent of the node we have found
                        XmlNode elmParent = node.ParentNode;
                        // Add the new element to the node we found
                        elmParent.AppendChild(elmNew);
                        // Specify the text of the new node
                        elmParent.LastChild.AppendChild(txtCatetory);
                        // Save the file
                        xmlDoc.Save(strFilename);
                    }
                }
            }

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

This would produce:

<?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>
    <Category>Comedy</Category>
  </Video>
  <Video>
    <Title>Her Alibi</Title>
    <Director>Bruce Beresford</Director>
    <Length>94 Mins</Length>
    <Format>DVD</Format>
    <Rating>PG-13</Rating>
  </Video>
  <Video>
    <Title>The Day After Tomorrow</Title>
    <Director>Roland Emmerich</Director>
    <Length>124 Minutes</Length>
    <Format>DVD</Format>
    <Rating>PG-13</Rating>
  </Video>
</Videos>

Using the same approach combined with what we learned about adding an item, you can add a new element that itself has child nodes. 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);

                // Get a reference to the root node
                XmlElement elmRoot = xmlDoc.DocumentElement;

                // Create a list of nodes whose name is Title
                XmlNodeList lstTitles = xmlDoc.GetElementsByTagName("Title");

                // visit each node named Title
                foreach(XmlNode node in lstTitles)
                {
                    // When you get to a node, look for the element's value
                // If you find an element whose value is The Day After Tomorrow
                    if (node.InnerText == "The Day After Tomorrow")
                    {
                        // Create an element named Actors
                        XmlElement elmNew = xmlDoc.CreateElement("Actors");
                        // Get a reference to the parent of the node we have found
                        XmlNode elmVideo = node.ParentNode;
                        // Add the new element to the node we found
                        elmVideo.AppendChild(elmNew);

                        // Create an element as a child of the new element
                        // Specify its name as Actor
                        elmNew = xmlDoc.CreateElement("Actor");
                        // Create the text of the new element
                        XmlText txtActor = xmlDoc.CreateTextNode("Dennis Quaid");
                        // Add the new Actor element to the Actors node
                        elmVideo.LastChild.AppendChild(elmNew);
                        // Specify the text of the new node
                        elmVideo.LastChild.LastChild.AppendChild(txtActor);

                        // In the same way, add the other Actor nodes
                        elmNew = xmlDoc.CreateElement("Actor");
                        txtActor = xmlDoc.CreateTextNode("Jake Gyllenhaal");
                        elmVideo.LastChild.AppendChild(elmNew);
                        elmVideo.LastChild.LastChild.AppendChild(txtActor);
                        
                        elmNew = xmlDoc.CreateElement("Actor");
                        txtActor = xmlDoc.CreateTextNode("Emmy Rossum");
                        elmVideo.LastChild.AppendChild(elmNew);
                        elmVideo.LastChild.LastChild.AppendChild(txtActor);

                        elmNew = xmlDoc.CreateElement("Actor");
                        txtActor = xmlDoc.CreateTextNode("Dash Mihok");
                        elmVideo.LastChild.AppendChild(elmNew);
                        elmVideo.LastChild.LastChild.AppendChild(txtActor);
                        
                        // Save the file
                        xmlDoc.Save(strFilename);
                    }
                }
            }

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

This would produce:

<?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>
    <Category>Comedy</Category>
  </Video>
  <Video>
    <Title>Her Alibi</Title>
    <Director>Bruce Beresford</Director>
    <Length>94 Mins</Length>
    <Format>DVD</Format>
    <Rating>PG-13</Rating>
    <Actors />
  </Video>
  <Video>
    <Title>The Day After Tomorrow</Title>
    <Director>Roland Emmerich</Director>
    <Length>124 Minutes</Length>
    <Format>DVD</Format>
    <Rating>PG-13</Rating>
    <Actors>
      <Actor>Dennis Quaid</Actor>
      <Actor>Jake Gyllenhaal</Actor>
      <Actor>Emmy Rossum</Actor>
      <Actor>Dash Mihok</Actor>
    </Actors>
  </Video>
</Videos>

You can also insert one or more elements as children of an existing node after locating that node. 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);

                // Get a reference to the root node
                XmlElement elmRoot = xmlDoc.DocumentElement;

                // Create a list of nodes whose names are Title
                XmlNodeList lstTitles = xmlDoc.GetElementsByTagName("Title");

                // visit each node named Title
                foreach(XmlNode node in lstTitles)
                {
                    // When you get to a node, look for the element's value
                    // If you find an element whose value is Her Alibi
                    if (node.InnerText == "Her Alibi")
                    {
                        // Get a reference to the video node that is 
                        // the parent of the video titled Her Alibi
                        XmlNode elmVideo = node.ParentNode;

                    // Create a list of the child nodes of the Her alibi video
                        XmlNodeList lstActors = elmVideo.ChildNodes;

                        // Visit each item of the collection
                        // looking for an element named Actors
                        foreach (XmlNode nodActor in lstActors)
                        {
                            // If you find an element named Actors
                            if (nodActor.Name == "Actors")
                            {
                                // Create a new element named Actor
                                // Specify its name as Actor
                         XmlElement elmNew = xmlDoc.CreateElement("Actor");
                                // Create the text of the new element
                         XmlText txtActor = xmlDoc.CreateTextNode("Tom Selleck");
                                // Add the new Actor element to the Actors node
                                elmVideo.LastChild.AppendChild(elmNew);
                                // Specify the text of the new node
                         elmVideo.LastChild.LastChild.AppendChild(txtActor);

                                // Add other Actor nodes
                                elmNew = xmlDoc.CreateElement("Actor");
                         txtActor = xmlDoc.CreateTextNode("Paulina Porizkova");
                                elmVideo.LastChild.AppendChild(elmNew);
                         elmVideo.LastChild.LastChild.AppendChild(txtActor);

                                elmNew = xmlDoc.CreateElement("Actor");
                         txtActor = xmlDoc.CreateTextNode("William Daniels");
                                elmVideo.LastChild.AppendChild(elmNew);
                         elmVideo.LastChild.LastChild.AppendChild(txtActor);

                                // Save the file
                                xmlDoc.Save(strFilename);

		// Stop, in this example, we don't expect another Actors node
                                break;
                            }
                        }
                    }
                }
            }

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

This would produce:

<?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>
    <Category>Comedy</Category>
  </Video>
  <Video>
    <Title>Her Alibi</Title>
    <Director>Bruce Beresford</Director>
    <Length>94 Mins</Length>
    <Format>DVD</Format>
    <Rating>PG-13</Rating>
    <Actors>
      <Actor>Tom Selleck</Actor>
      <Actor>Paulina Porizkova</Actor>
      <Actor>William Daniels</Actor>
    </Actors>
  </Video>
  <Video>
    <Title>The Day After Tomorrow</Title>
    <Director>Roland Emmerich</Director>
    <Length>124 Minutes</Length>
    <Format>DVD</Format>
    <Rating>PG-13</Rating>
    <Actors>
      <Actor>Dennis Quaid</Actor>
      <Actor>Jake Gyllenhaal</Actor>
      <Actor>Emmy Rossum</Actor>
      <Actor>Dash Mihok</Actor>
    </Actors>
  </Video>
</Videos>

Practical Learning: Adding Elements

In the Solution Explorer, right-click CollegeParkAutoParts3 -> Add -> New Item...
In the Templates list, make sure XML File is selected.
Set the Name to parts and click Add

Change the file as follows:

<?xml version="1.0" encoding="utf-8" ?>
<Parts>
	<Part>
		<PartNumber>293749</PartNumber>
		<Make>Acura</Make>
		<Model>MDX 3.5 4WD</Model>
		<CarYear>2005</CarYear>
		<PartName>Air Filter</PartName>
		<UnitPrice>16.85</UnitPrice>
	</Part>
	<Part>
		<PartNumber>283759</PartNumber>
		<Make>Audi</Make>
		<Model>A4 Quattro</Model>
		<CarYear>2002</CarYear>
		<PartName>Clutch Release Bearing</PartName>
		<UnitPrice>55.50</UnitPrice>
	</Part>
	<Part>
		<PartNumber>491759</PartNumber>
		<Make>Dodge</Make>
		<Model>Neon</Model>
		<CarYear>1998</CarYear>
		<PartName>Crankshaft Position Sensor</PartName>
		<UnitPrice>22.85</UnitPrice>
	</Part>
	<Part>
		<PartNumber>844509</PartNumber>
		<Make>Chevrolet</Make>
		<Model>Camaro</Model>
		<CarYear>2000</CarYear>
		<PartName>Control Module Connector</PartName>
		<UnitPrice>25.65</UnitPrice>
	</Part>
</Parts>

To save the file, on the main menu, click File -> Save parts.xml As...
Access the main folder of the current project and, inside of it, open a sub-folder of the same name (you should be in that folder already). In the sub-folder of the same name, open the bin sub-folder followed by the Release sub-folder. Click Save

To allow the user to create new parts, change the Program.cs file as follows:

using System;
using System.Xml;

namespace CollegeParkAutoParts3
{
    public static class Program
    {
        public static void CreateNewMake()
        {
            . . . No Change
        }

        public static void CreateNewModel()
        {
            . . . No Change
        }

        public 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(string[] args)
        {
            char mnuChoice = 'q';

            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
            {
                try
                {
                    Console.WriteLine("=-= Main Menu =-=");
                    Console.WriteLine("1 - Add New Car Make");
                    Console.WriteLine("2 - Add New Car Model");
                    Console.WriteLine("3 - Add New Part");
                    Console.WriteLine("0 - Exit");
                    Console.Write("Your Choice: ");
                    mnuChoice = char.Parse(Console.ReadLine());
                }
                catch (FormatException)
                {
                    Console.WriteLine("Invalid Choice");
                    Console.WriteLine("Please try again");
                }

                switch (mnuChoice)
                {
                    case '1':
                        CreateNewMake();
                        break;
                    case '2':
                        CreateNewModel();
                        break;
                    case '3':
                        AddNewPart();
                        break;
                    default:
                        break;
                }

                Console.WriteLine();
            } while((mnuChoice == '1') ||
                    (mnuChoice == '2') ||
                    (mnuChoice == '3') );

            Console.WriteLine("\nThank you!");
            return 0;
        }
    }
}

Execute the application and create the following parts:

Year	Make	Model	Part Name	Unit Price
1986	Acura	Integra	Alternator	110.75
1996	Dodge	Neon	Brake Pads	34.95
1996	Honda	Civic	Passenger Mirror	24.65
2002	Audi	A4 Quattro	Exhaust Gasket	1.55
1998	Honda	Civic	Brake Pads	34.85
2004	Dodge	Neon	Radiator Fan Assembly	125.95
2002	Audi	A4 Quattro	Axle Differential Bearing - Left	10.25
2000	Ford	Escort	Crankshaft Position Sensor	18.65
1998	Toyota	Corolla	Radiator	95.95
2004	Dodge	Neon	Oil Pump	112.85
2004	Honda	Civic	Oxygen Sensor	90.55
2000	Ford	Escort	Right Caliper Assembly Front	32.85
2004	Dodge	Neon	Exhaust Valve	5.85
2002	Audi	A4 Quattro	Alternator	305.50
1986	Acura	Integra	Fuel Cap (Regular)	4.15
2004	Dodge	Neon	Clutch Release Bearing	25.75
2002	Dodge	Dakota	Starter Motor	145.95
2002	Acura	NSX	Oil Filter	7.05
1998	BMW	325I	Rack and Pinion Bellow Kit	19.25
2001	Acura	Integra	Voltage Regulator	215.75
2002	Audi	A4 Quattro	Muffler Hanger	3.35
2002	Acura	NSX	Oil Drain Plug	1.35
2002	Dodge	Dakota	Circuit Breaker	3.25
2004	Dodge	Neon	Brake Pad	20.55
2004	Honda	Civic	Fusible Link	3.35
2002	Dodge	Dakota	Circuit Breaker	3.45
2004	Honda	Civic	Differential Bearing	36.75
1998	Toyota	Corolla	Thermostat Standard Temperature	9.35
2002	Audi	A4 Quattro	Cooling Fan Sensor	8.65
2002	Acura	NSX	Oil Pump Seal	12.55
2004	Dodge	Neon	Master Cylinder w/o ABS w/2 Wheel	102.95
2002	Acura	NSX	Valve Stem Oil Seal	1.75
2002	Dodge	Dakota	Fuse	0.40
1998	Toyota	Corolla	Regular Thermostat	11.15

Close the DOS window

Insertion an Element Referencing a Sibling

Instead of simply adding a new node at the end of child nodes, you can specify any other position you want. For example, you may want the new node to precede an existing child node. To support this operation, the XmlNode class provides the InsertBefore() method. Its syntax is:

public virtual XmlNode InsertBefore(XmlNode newChild, XmlNode refChild);

The first argument of this method is the new node that will be added. The second argument is the sibling that will succeed the new node. Consider the following version of our Videos.xml file:

<?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>
    <Category>Comedy</Category>
  </Video>
  <Video>
    <Title>Her Alibi</Title>
    <Director>Bruce Beresford</Director>
    <Length>94 Mins</Length>
    <Format>DVD</Format>
    <Rating>PG-13</Rating>
  </Video>
  <Video>
    <Title>Fatal Attraction</Title>
    <Director>Adrian Lyne</Director>
    <Length>119 Minutes</Length>
    <Format>DVD</Format>
    <Rating>R</Rating>
  </Video>
  <Video>
    <Title>The Day After Tomorrow</Title>
    <Director>Roland Emmerich</Director>
    <Length>124 Minutes</Length>
    <Format>DVD</Format>
    <Rating>PG-13</Rating>
  </Video>
</Videos>

Imagine you want to create a new Category element below the Director element whose name is Adrian Lyne. You can first get a list of videos. Inside of each video, check the nodes and find out whether the video has a Director node whose text is Adrian Lyne. Once you find that node, you can add the new element after 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))
            {
                xmlDoc.Load(strFilename);

                // Get a reference to the root node
                XmlElement elmRoot = xmlDoc.DocumentElement;

                // Create a list of the videos
                XmlNodeList lstVideos = xmlDoc.GetElementsByTagName("Video");

                // visit each video
                foreach (XmlNode node in lstVideos)
                {
                    // Within a video, create a list of its children
                    XmlNodeList lstChildren = node.ChildNodes;

                    // Visit each child node
                    foreach (XmlNode dir in lstChildren)
                    {
                 // If the child node is (a director and its name is) Adrian Lyne
                        if (dir.InnerText == "Adrian Lyne")
                        {
                            // Create an element named Category
                            XmlElement elmNew = xmlDoc.CreateElement("Category");
                            // Specify the text of the new element
                            elmNew.InnerText = "Drama";
                            
                 // Insert the new node below the Adrian Lyne node Director
                            node.InsertAfter(elmNew, dir);

                            // Save the file
                            xmlDoc.Save(strFilename);

                            // Stop
                            break;
                        }
                    }
                }
            }

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

This would produce:

<?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>
    <Category>Comedy</Category>
  </Video>
  <Video>
    <Title>Her Alibi</Title>
    <Director>Bruce Beresford</Director>
    <Length>94 Mins</Length>
    <Format>DVD</Format>
    <Rating>PG-13</Rating>
  </Video>
  <Video>
    <Title>Fatal Attraction</Title>
    <Director>Adrian Lyne</Director>
    <Category>Drama</Category>
    <Length>119 Minutes</Length>
    <Format>DVD</Format>
    <Rating>R</Rating>
  </Video>
  <Video>
    <Title>The Day After Tomorrow</Title>
    <Director>Roland Emmerich</Director>
    <Length>124 Minutes</Length>
    <Format>DVD</Format>
    <Rating>PG-13</Rating>
  </Video>
</Videos>

In the same way, you can insert a new node after a child of a child (of a child of a child of a child) of any node.

If you want to new node to be positioned after an existing child node, you can call the XmlNode.InsertAfter() method. Its syntax is:

public virtual XmlNode InsertAfter(XmlNode newChild, XmlNode refChild);

Node Removal

If you have a node you don't want or don't need anymore in the file, you can delete it. To delete a node, the XmlNode class provides the RemoveChild() method. Its syntax is:

public virtual XmlNode RemoveChild(XmlNode oldChild);

This method takes as argument the node to delete. If the node exists, it would be deleted and the method would return it. If the node doesn't exist, nothing would happen. To effectively use this method, you should first locate the particular node you want to delete. You can look for it using any of the logics we have applied so far. Once you find the node, you can then delete it. Imagine you want to delete a node whose name is Director and whose value is Bruce Beresford. Here is an example of calling this method to perform the operation:

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);

                // Get a reference to the root node
                XmlElement elmRoot = xmlDoc.DocumentElement;

                // Create a list of the videos
                XmlNodeList lstVideos = xmlDoc.GetElementsByTagName("Video");

                // visit each video
                foreach (XmlNode node in lstVideos)
                {
                    // Within a video, create a list of its children
                    XmlNodeList lstChildren = node.ChildNodes;

                    // Visit each child node
                    foreach (XmlNode dir in lstChildren)
                    {
                        // If the child node is Bruce Beresford
                        if (dir.InnerText == "Bruce Beresford")
                        {
                            node.RemoveChild(dir);
     
                            // Save the file
                            xmlDoc.Save(strFilename);

                            // Stop
                            break;
                        }
                    }
                }
            }

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

To delete all child nodes of a node, you can call the XmlNode.RemoveAll() method. Its syntax is:

public virtual void RemoveAll();

When called, this method will remove all child nodes, if any, of their parent node.


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