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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)

public event UnreferencedObjectEventHandler UnreferencedObject

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>

using System;
using System.IO;
using System.Text;
using System.Xml;
using System.Xml.Serialization;
using System.Xml.Schema;

// You must use the SoapIncludeAttribute to inform the XmlSerializer
// that the Vehicle type should be recognized when deserializing.
[SoapInclude(typeof(Vehicle))]
public class Group
{
   public string GroupName;
   public Vehicle GroupVehicle;
}
 [SoapInclude(typeof(Vehicle))]
public class Vehicle
{
   public string licenseNumber;
}

public class Run
{
   public static void Main()
   {
      Run test = new Run();
      test.DeserializeObject("UnrefObj.xml");
   }

   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
      (Serializer_UnreferencedObject);

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

      // Deserialize and cast the object.
      Group myGroup; 
      myGroup = (Group) mySerializer.Deserialize(reader);
      reader.ReadEndElement();
      reader.Close();
   }

   private void Serializer_UnreferencedObject
   (object sender, UnreferencedObjectEventArgs e){
      Console.WriteLine("UnreferencedObject:");
      Console.WriteLine("ID: " + e.UnreferencedId);
      Console.WriteLine("UnreferencedObject: " + e.UnreferencedObject);
      Vehicle myVehicle = (Vehicle) e.UnreferencedObject;
      Console.WriteLine("License: " + myVehicle.licenseNumber);
   }
}

// The file named "UnrefObj.xml" should contain this 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>



.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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

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