XmlSerializer.UnknownElement Event

 
System_CAPS_noteNote

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Occurs when the XmlSerializer encounters an XML element of unknown type during deserialization.

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

Public Event UnknownElement As XmlElementEventHandler

By default, after calling the Deserialize method, the XmlSerializer ignores XML attributes of unknown types. However, you can use this event to handle such node types.

System_CAPS_noteNote

If the XmlAnyElementAttribute is applied to a field that returns an array of XmlElement objects, all unknown elements are collected in the array. In that case, the UnknownElement event does not occur.

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 following XML code 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>
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

.NET Framework
Available since 1.1
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