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XmlElementAttribute Constructor (String, Type)

Initializes a new instance of the XmlElementAttribute and specifies the name of the XML element and a derived type for the member to which the XmlElementAttribute is applied. This member type is used when the XmlSerializer serializes the object that contains it.

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

public XmlElementAttribute(
	string elementName,
	Type type
)

Parameters

elementName
Type: System.String

The XML element name of the serialized member.

type
Type: System.Type

The Type of an object derived from the member's type.

By default, the XmlSerializer uses the member name as the XML element name when serializing a class instance. For example, a field named Vehicle generates an XML element named Vehicle. However, if you need a different element, such as Cars, pass it in the elementName parameter.

Use the type parameter to specify a type that is derived from a base class. For example, suppose a property named MyAnimal returns an Animal object. You want to enhance the object, so you create a new class named Mammal that inherits from the Animal class. To instruct the XmlSerializer to accept the Mammal class when it serializes the MyAnimal property, pass the Type of the Mammal class to the constructor.

The following example serializes a class named Orchestra that contains a single field named Instruments, which returns an array of Instrument objects. A second class named Brass inherits from the Instrument class. The example applies the XmlElementAttribute to the Instruments field, and specifies the Brass type, allowing the Instruments field to accept Brass objects. The example also specifies the name of the XML element by setting the ElementName property.

using System;
using System.IO;
using System.Xml.Serialization;

public class Orchestra
{
   public Instrument[] Instruments;
}   

public class Instrument
{
   public string Name;
}

public class Brass:Instrument{
   public bool IsValved;
}

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

    public void SerializeObject(string filename)
    {
      // To write the file, a TextWriter is required.
      TextWriter writer = new StreamWriter(filename);

      XmlAttributeOverrides attrOverrides = 
         new XmlAttributeOverrides();
      XmlAttributes attrs = new XmlAttributes();

      // Creates an XmlElementAttribute that overrides the Instrument type.
      XmlElementAttribute attr = new 
      XmlElementAttribute(typeof(Brass));
      attr.ElementName = "Brass";

      // Adds the element to the collection of elements.
      attrs.XmlElements.Add(attr);
      attrOverrides.Add(typeof(Orchestra), "Instruments", attrs);

      // Creates the XmlSerializer using the XmlAttributeOverrides.
      XmlSerializer s = 
      new XmlSerializer(typeof(Orchestra), attrOverrides);

      // Creates the object to serialize.
      Orchestra band = new Orchestra();

      // Creates an object of the derived type.
      Brass i = new Brass();
      i.Name = "Trumpet";
      i.IsValved = true;
      Instrument[] myInstruments = {i};
      band.Instruments = myInstruments;
      s.Serialize(writer,band);
      writer.Close();
   }

   public void DeserializeObject(string filename)
   {
      XmlAttributeOverrides attrOverrides = 
         new XmlAttributeOverrides();
      XmlAttributes attrs = new XmlAttributes();

      // Creates an XmlElementAttribute that override the Instrument type.
      XmlElementAttribute attr = new 
      XmlElementAttribute(typeof(Brass));
      attr.ElementName = "Brass";

      // Adds the element to the collection of elements.
      attrs.XmlElements.Add(attr);
      attrOverrides.Add(typeof(Orchestra), "Instruments", attrs);

      // Creates the XmlSerializer using the XmlAttributeOverrides.
      XmlSerializer s = 
      new XmlSerializer(typeof(Orchestra), attrOverrides);

      FileStream fs = new FileStream(filename, FileMode.Open);
      Orchestra band = (Orchestra) s.Deserialize(fs);
      Console.WriteLine("Brass:");

      /* Deserializing differs from serializing. To read the 
         derived-object values, declare an object of the derived 
         type (Brass) and cast the Instrument instance to it. */
      Brass b;
      foreach(Instrument i in band.Instruments) 
      {
         b= (Brass)i;
         Console.WriteLine(
         b.Name + "\n" + 
         b.IsValved);
      }
   }
}

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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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