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XmlElementEventHandler Delegate

Represents the method that will handle the UnknownElement event of an XmlSerializer.

[Visual Basic]
<Serializable>
Public Delegate Sub XmlElementEventHandler( _
   ByVal sender As Object, _
   ByVal e As XmlElementEventArgs _
)
[C#]
[Serializable]
public delegate void XmlElementEventHandler(
   object sender,
   XmlElementEventArgs e
);
[C++]
[Serializable]
public __gc __delegate void XmlElementEventHandler(
   Object* sender,
   XmlElementEventArgs* e
);

[JScript] In JScript, you can use the delegates in the .NET Framework, but you cannot define your own.

Parameters [Visual Basic, C#, C++]

The declaration of your event handler must have the same parameters as the XmlElementEventHandler delegate declaration.

Remarks

When you create an XmlElementEventHandler delegate, you identify the method that will handle the event. To associate the event with your event handler, add an instance of the delegate to the event. The event handler is called whenever the event occurs, unless you remove the delegate. For more information about event handler delegates, see Events and Delegates.

The UnknownElement event can occur only when you call the Deserialize method.

Example

[Visual Basic, C#, C++] The following example deserializes a class named Group from a file named UnknownElements.xml. Whenever an element is found in the file that has no corresponding member in the class, the UnknownElement event occurs. To try the example, paste the XML code below into a file named UnknownElements.xml.

<?xml version="1.0" encoding="utf-8"?>
<Group xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <GroupName>MyGroup</GroupName>
  <GroupSize>Large</GroupSize>
  <GroupNumber>444</GroupNumber>
  <GroupBase>West</GroupBase>
</Group>
[Visual Basic] 
Imports System
Imports System.IO
Imports System.Xml.Serialization
Imports System.Xml
Imports System.Xml.Schema
Imports Microsoft.VisualBasic

Public Class Group
   Public GroupName As String 
End Class

Public Class Test
   Shared Sub Main()
      Dim t As Test = new Test()
      ' Deserialize the file containing unknown elements.
      t.DeserializeObject("UnknownElements.xml")
   End Sub

   Private Sub Serializer_UnknownElement _
   (sender As Object , e As XmlElementEventArgs)
      Console.WriteLine("Unknown Element")
      Console.WriteLine(ControlChars.Tab & e.Element.Name + " " & e.Element.InnerXml)
      Console.WriteLine(ControlChars.Tab & e.LineNumber & ":"  & e.LineNumber)
      Console.WriteLine(ControlChars.Tab & e.LinePosition & ":"   & e.LinePosition)
      
      Dim x As Group = CType( e.ObjectBeingDeserialized, Group)
      Console.WriteLine (x.GroupName)
      Console.WriteLine (sender.ToString())
   End Sub
   
   Private Sub DeserializeObject(filename As String)
      Dim ser As XmlSerializer = new XmlSerializer(GetType(Group))
      ' Add a delegate to handle unknown element events.
      AddHandler ser.UnknownElement, _
      AddressOf Serializer_UnknownElement 
      ' A FileStream is needed to read the XML document.
     Dim fs As FileStream  = new FileStream(filename, FileMode.Open)
     Dim g  As Group = CType(ser.Deserialize(fs),Group)
     fs.Close()
   End Sub
End Class

[C#] 
using System;
using System.IO;
using System.Xml.Serialization;
using System.Xml;
using System.Xml.Schema;

public class Group{
   public string GroupName;
}

public class Test{
   static void Main(){
      Test t = new Test();
      // Deserialize the file containing unknown elements.
      t.DeserializeObject("UnknownElements.xml");
   }
   private void Serializer_UnknownElement(object sender, XmlElementEventArgs e){
      Console.WriteLine("Unknown Element");
      Console.WriteLine("\t" + e.Element.Name + " " + e.Element.InnerXml);
      Console.WriteLine("\t LineNumber: " + e.LineNumber);
      Console.WriteLine("\t LinePosition: " + e.LinePosition);
      
      Group x  = (Group) e.ObjectBeingDeserialized;
      Console.WriteLine (x.GroupName);
      Console.WriteLine (sender.ToString());
   }
   private void DeserializeObject(string filename){
      XmlSerializer ser = new XmlSerializer(typeof(Group));
      // Add a delegate to handle unknown element events.
      ser.UnknownElement+=new XmlElementEventHandler(Serializer_UnknownElement);
      // A FileStream is needed to read the XML document.
     FileStream fs = new FileStream(filename, FileMode.Open);
     Group g = (Group) ser.Deserialize(fs);
     fs.Close();
       }
}

[C++] 
#using <mscorlib.dll>
#using <System.Xml.dll>
using namespace System;
using namespace System::IO;
using namespace System::Xml::Serialization;
using namespace System::Xml;
using namespace System::Xml::Schema;

__gc public class Group
{
public:
   String* GroupName;
};

__gc public class Test
{
public:
   void Serializer_UnknownElement(Object* sender, XmlElementEventArgs * e) 
   {
      Console::WriteLine(S"Unknown Element");
      Console::Write(S"\t {0}", e -> Element -> Name);
      Console::WriteLine(S" {0}", e -> Element -> InnerXml);
      Console::WriteLine(S"\t LineNumber: {0}", __box(e -> LineNumber));
      Console::WriteLine(S"\t LinePosition: {0}", __box(e -> LinePosition));

      Group *x  = dynamic_cast<Group*>(e -> ObjectBeingDeserialized);
      Console::WriteLine (x -> GroupName);
      Console::WriteLine (sender);
   }
   void DeserializeObject(String* filename)
   {
      XmlSerializer* ser = new XmlSerializer(__typeof(Group));
      // Add a delegate to handle unknown element events.
      ser -> UnknownElement += new XmlElementEventHandler(this, &Test::Serializer_UnknownElement);
      // A FileStream is needed to read the XML document.
      FileStream* fs = new FileStream(filename, FileMode::Open);
      Group *g = dynamic_cast<Group*>(ser -> Deserialize(fs));
      fs -> Close();
   }
};

int main()
{
   Test* t = new Test();
   // Deserialize the file containing unknown elements.
   t -> DeserializeObject(S"UnknownElements.xml");
}

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Namespace: System.Xml.Serialization

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

Assembly: System.Xml (in System.Xml.dll)

See Also

System.Xml.Serialization Namespace

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