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XmlSerializer.UnreferencedObject Event

Occurs during deserialization of a SOAP-encoded XML stream, when the XmlSerializer encounters a recognized type that is not used or is unreferenced.

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

'Declaration
Public Event UnreferencedObject As UnreferencedObjectEventHandler
'Usage
Dim instance As XmlSerializer 
Dim handler As UnreferencedObjectEventHandler 

AddHandler instance.UnreferencedObject, handler

The UnreferencedObject event only occurs when the XmlSerializer is used to deserialize an XML document that contains a SOAP message that conforms to section 5 of the World Wide Web Consortium (www.w3.org) document, "Simple Object Access Protocol (SOAP) 1.1".

Documents that conform to section 5 are in a special format. At the very least, such a document includes the main body of the SOAP message. However, rather than having all types defined inline in the document, some type definitions can be encoded as references to top-level elements in the document. Thus, for every element found in the main body that is a reference, there must be a corresponding element that contains the type definition. To correlate the referencing element and the type definition, the type definition has an id attribute set to a unique string ID and the referencing element has an href attribute that references the same ID.

 <Group xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" id="id1" n1:GroupName=".NET" GroupNumber="ZDI=" CreationDate="2002-05-02" xmlns:n1="http:'www.cpandl.com">
     <PosInt xsi:type="xsd:nonNegativeInteger">10000</PosInt>
     <GroupVehicle href="#id2" />
   </Group>
   <Vehicle id="id2" n1:type="Vehicle" xmlns:n1="http://www.w3.org/2001/XMLSchema-instance">
     <licenseNumber xmlns:q1="http://www.w3.org/2001/XMLSchema" n1:type="q1:string">1234</licenseNumber>
   </Vehicle>

The UnreferencedObject event occur when there is a type definition found in the document, but no parameter in the main body references it. When the event occurs, you can retrieve the XML type of the unreferenced object by examining the UnreferencedObject property of the UnreferencedObjectEventArgs class. The XML ID of the object is returned by the UnreferencedId property.

The UnreferencedObject event should not be confused with the UnknownElement and UnknownNode events, which occur when there is no class member that corresponds to the XML node or element type.

The following example adds an UnreferencedObjectEventHandler to an XmlSerializer. The event is handled by the Serializer_UnreferencedObject method. To run the example, cut and paste the following XML into a file named "UnrefObj.xml".

 <wrapper>
   <Group xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" id="id1" n1:GroupName=".NET" xmlns:n1="http://www.cpandl.com">
    </Group>
 <Vehicle id="id2" n1:type="Vehicle" xmlns:n1="http://www.w3.org/2001/XMLSchema-instance">
     <licenseNumber xmlns:q1="http://www.w3.org/2001/XMLSchema" n1:type="q1:string">ABCD</licenseNumber>
   </Vehicle>
 <Vehicle id="id3" n1:type="Vehicle" xmlns:n1="http://www.w3.org/2001/XMLSchema-instance">
     <licenseNumber xmlns:q1="http://www.w3.org/2001/XMLSchema" n1:type="q1:string">1234</licenseNumber>
   </Vehicle>
 </wrapper>
Imports System
Imports System.IO
Imports System.Text
Imports System.Xml
Imports System.Xml.Serialization
Imports System.Xml.Schema

' You must use the SoapIncludeAttribute to inform the XmlSerializer 
' that the Vehicle type should be recognized when deserializing.
<SoapInclude(GetType(Vehicle))> _
Public Class Group
    Public GroupName As String 
   public GroupVehicle As Vehicle 
End Class 

Public Class Vehicle
   Public licenseNumber As String  
End Class 


Public Class Run
   Shared Sub Main()
      Dim test As Run = new Run()
      test.DeserializeObject("UnrefObj.xml")
   End Sub 

   Public Sub DeserializeObject(filename As String)
      ' Create an instance of the XmlSerializer class. 
      Dim myMapping As XmlTypeMapping = _
      (new SoapReflectionImporter().ImportTypeMapping _
      (GetType(Group)))
      Dim mySerializer As XmlSerializer =  _
      new XmlSerializer(myMapping)

      AddHandler mySerializer.UnreferencedObject, _
      AddressOf Serializer_UnreferencedObject

      ' Reading the file requires an  XmlTextReader. 
      Dim reader As XmlTextReader = _
      new XmlTextReader(filename)
      reader.ReadStartElement()

      ' Deserialize and cast the object. 
      Dim myGroup As Group  
      myGroup = CType( mySerializer.Deserialize(reader), Group)
      reader.ReadEndElement()
      reader.Close()
   End Sub 

   Private Sub Serializer_UnreferencedObject _
   (sender As object , e As UnreferencedObjectEventArgs)
      Console.WriteLine("UnreferencedObject:")
      Console.WriteLine("ID: " + e.UnreferencedId)
      Console.WriteLine("UnreferencedObject: " + e.UnreferencedObject)
      Dim myVehicle As Vehicle = CType(e.UnreferencedObject, Vehicle)
      Console.WriteLine("License: " + myVehicle.licenseNumber)
       End Sub 
 End Class 

' The XML document should contain this information: 

'<wrapper> 

'  <Group xmlns:xsi="http:'www.w3.org/2001/XMLSchema-instance"  
'xmlns:xsd="http:'www.w3.org/2001/XMLSchema" id="id1"  
'n1:GroupName=".NET" xmlns:n1="http:'www.cpandl.com"> 
'   </Group> 

'<Vehicle id="id2" n1:type="Vehicle"  
'xmlns:n1="http:'www.w3.org/2001/XMLSchema-instance"> 
'    <licenseNumber xmlns:q1="http:'www.w3.org/2001/XMLSchema"  
'n1:type="q1:string">ABCD</licenseNumber> 
'  </Vehicle> 

'<Vehicle id="id3" n1:type="Vehicle"  
'xmlns:n1="http:'www.w3.org/2001/XMLSchema-instance"> 
'    <licenseNumber xmlns:q1="http:'www.w3.org/2001/XMLSchema"  
'n1:type="q1:string">1234</licenseNumber> 
'  </Vehicle> 

'</wrapper>
#using <mscorlib.dll>
#using <System.Xml.dll>
using namespace System;
using namespace System::IO;
using namespace System::Text;
using namespace System::Xml;
using namespace System::Xml::Serialization;
using namespace System::Xml::Schema;

__gc public class Vehicle;
[SoapInclude(__typeof(Vehicle))]
__gc public class Vehicle
{
public:
   String* licenseNumber;
};

// You must use the SoapIncludeAttribute to inform the XmlSerializer
// that the Vehicle type should be recognized when deserializing.
[SoapInclude(__typeof(Vehicle))]
__gc public class Group
{
public:
   String* GroupName;
   Vehicle * GroupVehicle;
};

__gc public class Run 
{
public:
   void DeserializeObject(String* filename) 
   {
      // Create an instance of the XmlSerializer class.
      XmlTypeMapping * myMapping = 
         ((new SoapReflectionImporter()) -> ImportTypeMapping(__typeof(Group)));
      XmlSerializer* mySerializer = new XmlSerializer(myMapping);

      mySerializer -> UnreferencedObject += new UnreferencedObjectEventHandler
         (this, &Run::Serializer_UnreferencedObject);

      // Reading the file requires an  XmlTextReader.
      XmlTextReader* reader = new XmlTextReader(filename);
      reader -> ReadStartElement();

      // Deserialize and cast the object.
      Group * myGroup; 
      myGroup = dynamic_cast<Group*>(mySerializer -> Deserialize(reader));
      reader -> ReadEndElement();
      reader -> Close();
   }

private:
   void Serializer_UnreferencedObject(Object* /*sender*/, UnreferencedObjectEventArgs * e) 
   {
      Console::WriteLine(S"UnreferencedObject:");
      Console::WriteLine(S"ID: {0}", e -> UnreferencedId);
      Console::WriteLine(S"UnreferencedObject: {0}", e -> UnreferencedObject);
      Vehicle * myVehicle = dynamic_cast<Vehicle*>(e -> UnreferencedObject);
      Console::WriteLine(S"License: {0}", myVehicle -> licenseNumber);
   }
};

int main() 
{
   Run* test = new Run();
   test -> DeserializeObject(S"UnrefObj.xml");
}


// The file named S"UnrefObj.xml" should contain this XML:

// <wrapper>

//  <Group xmlns:xsi=S"http://www.w3.org/2001/XMLSchema-instance" 
//xmlns:xsd=S"http://www.w3.org/2001/XMLSchema" id=S"id1" 
//n1:GroupName=S".NET" xmlns:n1=S"http://www.cpandl.com">
//   </Group>

//<Vehicle id=S"id2" n1:type=S"Vehicle" 
//xmlns:n1=S"http://www.w3.org/2001/XMLSchema-instance">
//   <licenseNumber xmlns:q1=S"http://www.w3.org/2001/XMLSchema" 
//n1:type=S"q1:String*">ABCD</licenseNumber>
//   </Vehicle>

//<Vehicle id=S"id3" n1:type=S"Vehicle" 
//xmlns:n1=S"http://www.w3.org/2001/XMLSchema-instance">
//    <licenseNumber xmlns:q1=S"http://www.w3.org/2001/XMLSchema" 
//n1:type=S"q1:String*">1234</licenseNumber>
//  </Vehicle>

//</wrapper>

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0

XNA Framework

Supported in: 3.0, 2.0, 1.0
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