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XmlAttributes Class

Represents a collection of attribute objects that control how the XmlSerializer serializes and deserializes an object.

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

public ref class XmlAttributes
public class XmlAttributes
public class XmlAttributes
Not applicable.

Creating the XmlAttributes is part of a process that overrides the default way the XmlSerializer serializes class instances. For example, suppose you want to serialize an object that is created from a DLL which has an inaccessible source. By using the XmlAttributeOverrides, you can augment or otherwise control how the object is serialized.

The members of the XmlAttributes class correspond directly to a family of attribute classes that control serialization. For example, the XmlText property must be set to an XmlTextAttribute, which allows you to override serialization of a field or property by instructing the XmlSerializer to serialize the property value as XML text. For a complete list of attributes that control serialization, see the XmlSerializer.

For more details on using the XmlAttributeOverrides with the XmlAttributes class, see How to: Specify an Alternate Element Name for an XML Stream.

The following example serializes an instance of a class named Orchestra, which contains a single field named Instruments that returns an array of Instrument objects. A second class named Brass inherits from the Instrument class. The example creates an XmlAttributes object to override the Instrument field--allowing the field to accept Brass objects--and adds the XmlAttributes object to an instance of the XmlAttributeOverrides class.

#using <System.Xml.dll>
#using <System.dll>

using namespace System;
using namespace System::IO;
using namespace System::Xml::Serialization;
public ref class Instrument
{
public:
   String^ Name;
};

public ref class Brass: public Instrument
{
public:
   bool IsValved;
};

public ref class Orchestra
{
public:
   array<Instrument^>^Instruments;
};

void SerializeObject( String^ filename )
{
   /* Each overridden field, property, or type requires 
      an XmlAttributes object. */
   XmlAttributes^ attrs = gcnew XmlAttributes;

   /* Create an XmlElementAttribute to override the 
      field that returns Instrument objects. The overridden field
      returns Brass objects instead. */
   XmlElementAttribute^ attr = gcnew XmlElementAttribute;
   attr->ElementName = "Brass";
   attr->Type = Brass::typeid;

   // Add the element to the collection of elements.
   attrs->XmlElements->Add( attr );

   // Create the XmlAttributeOverrides object.
   XmlAttributeOverrides^ attrOverrides = gcnew XmlAttributeOverrides;

   /* Add the type of the class that contains the overridden 
      member and the XmlAttributes to override it with to the 
      XmlAttributeOverrides object. */
   attrOverrides->Add( Orchestra::typeid, "Instruments", attrs );

   // Create the XmlSerializer using the XmlAttributeOverrides.
   XmlSerializer^ s = gcnew XmlSerializer( Orchestra::typeid,attrOverrides );

   // Writing the file requires a TextWriter.
   TextWriter^ writer = gcnew StreamWriter( filename );

   // Create the object that will be serialized.
   Orchestra^ band = gcnew Orchestra;

   // Create an object of the derived type.
   Brass^ i = gcnew Brass;
   i->Name = "Trumpet";
   i->IsValved = true;
   array<Instrument^>^myInstruments = {i};
   band->Instruments = myInstruments;

   // Serialize the object.
   s->Serialize( writer, band );
   writer->Close();
}

void DeserializeObject( String^ filename )
{
   XmlAttributeOverrides^ attrOverrides = gcnew XmlAttributeOverrides;
   XmlAttributes^ attrs = gcnew XmlAttributes;

   // Create an XmlElementAttribute to override the Instrument.
   XmlElementAttribute^ attr = gcnew XmlElementAttribute;
   attr->ElementName = "Brass";
   attr->Type = Brass::typeid;

   // Add the element to the collection of elements.
   attrs->XmlElements->Add( attr );
   attrOverrides->Add( Orchestra::typeid, "Instruments", attrs );

   // Create the XmlSerializer using the XmlAttributeOverrides.
   XmlSerializer^ s = gcnew XmlSerializer( Orchestra::typeid,attrOverrides );
   FileStream^ fs = gcnew FileStream( filename,FileMode::Open );
   Orchestra^ band = dynamic_cast<Orchestra^>(s->Deserialize( fs ));
   Console::WriteLine( "Brass:" );

   /* The difference between deserializing the overridden 
      XML document and serializing it is this: To read the derived 
      object values, you must declare an object of the derived type 
      (Brass), and cast the Instrument instance to it. */
   Brass^ b;
   System::Collections::IEnumerator^ myEnum = band->Instruments->GetEnumerator();
   while ( myEnum->MoveNext() )
   {
      Instrument^ i = safe_cast<Instrument^>(myEnum->Current);
      b = dynamic_cast<Brass^>(i);
      Console::WriteLine( "{0}\n{1}", b->Name, b->IsValved );
   }
}

int main()
{
   SerializeObject( "Override.xml" );
   DeserializeObject( "Override.xml" );
}

import System.*;
import System.IO.*;
import System.Xml.Serialization.*;

public class Orchestra
{
    public Instrument instruments[];
} //Orchestra

public class Instrument
{
    public String name;
} //Instrument

public class Brass extends Instrument
{
    public boolean isValved;
} //Brass

public class Run
{
    public static void main(String[] args)
    {
        Run test = new Run();
        test.SerializeObject("Override.xml");
        test.DeserializeObject("Override.xml");
    } //main

    public void SerializeObject(String fileName)
    {
        /* Each overridden field, property, or type requires 
           an XmlAttributes object. */
        XmlAttributes attrs = new XmlAttributes();

        /* Create an XmlElementAttribute to override the 
           field that returns Instrument objects. The overridden field
           returns Brass objects instead. */
        XmlElementAttribute attr = new XmlElementAttribute();
        attr.set_ElementName("Brass");
        attr.set_Type(Brass.class.ToType());

        // Add the element to the collection of elements.
        attrs.get_XmlElements().Add(attr);

        // Create the XmlAttributeOverrides object.
        XmlAttributeOverrides attrOverrides = new XmlAttributeOverrides();

        /* Add the type of the class that contains the overridden 
           member and the XmlAttributes to override it with to the 
           XmlAttributeOverrides object. */
        attrOverrides.Add(Orchestra.class.ToType(), "instruments", attrs);

        // Create the XmlSerializer using the XmlAttributeOverrides.
        XmlSerializer s =
            new XmlSerializer(Orchestra.class.ToType(), attrOverrides);

        // Writing the file requires a TextWriter.
        TextWriter writer = new StreamWriter(fileName);

        // Create the object that will be serialized.
        Orchestra band = new Orchestra();

        // Create an object of the derived type.
        Brass i = new Brass();
        i.name = "Trumpet";
        i.isValved = true;
        Instrument myInstruments[] = { i };
        band.instruments = myInstruments;

        // Serialize the object.
        s.Serialize(writer, band);
        writer.Close();
    } //SerializeObject

    public void DeserializeObject(String fileName)
    {
        XmlAttributeOverrides attrOverrides = new XmlAttributeOverrides();
        XmlAttributes attrs = new XmlAttributes();

        // Create an XmlElementAttribute to override the Instrument.
        XmlElementAttribute attr = new XmlElementAttribute();
        attr.set_ElementName("Brass");
        attr.set_Type(Brass.class.ToType());

        // Add the element to the collection of elements.
        attrs.get_XmlElements().Add(attr);
        attrOverrides.Add(Orchestra.class.ToType(), "instruments", attrs);

        // Create the XmlSerializer using the XmlAttributeOverrides.
        XmlSerializer s =
            new XmlSerializer(Orchestra.class.ToType(), attrOverrides);
        FileStream fs = new FileStream(fileName, FileMode.Open);
        Orchestra band = (Orchestra)s.Deserialize(fs);
        Console.WriteLine("Brass:");

        /* The difference between deserializing the overridden 
           XML document and serializing it is this: To read the derived 
           object values, you must declare an object of the derived type 
           (Brass), and cast the Instrument instance to it. */
        Brass b;
        for (int iCtr = 0; iCtr < band.instruments.length; iCtr++) {
            Instrument i = band.instruments[iCtr];
            b = (Brass)i;
            Console.WriteLine(b.name + "\n" + Convert.ToString(b.isValved));
        }
    } //DeserializeObject
} //Run

System.Object
  System.Xml.Serialization.XmlAttributes

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0

XNA Framework

Supported in: 1.0

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