XmlAttributes Class

Definition

public ref class XmlAttributes

public class XmlAttributes

type XmlAttributes = class

Public Class XmlAttributes

Inheritance

Object

XmlAttributes

Examples

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;
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)
 {
 /* 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.ElementName = "Brass";
 attr.Type = typeof(Brass);

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

 // Create the XmlSerializer using the XmlAttributeOverrides.
 XmlSerializer s =
 new XmlSerializer(typeof(Orchestra), 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();
 }

 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.ElementName = "Brass";
 attr.Type = typeof(Brass);

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

 attrOverrides.Add(typeof(Orchestra), "Instruments", attrs);

 // Create 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:");

 /* 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;
 foreach(Instrument i in band.Instruments)
 {
 b = (Brass)i;
 Console.WriteLine(
 b.Name + "\n" +
 b.IsValved);
 }
 }
}

Imports System.IO
Imports System.Xml.Serialization

Public Class Orchestra
 Public Instruments() As Instrument
End Class

Public Class Instrument
 Public Name As String
End Class

Public Class Brass
 Inherits Instrument
 Public IsValved As Boolean
End Class


Public Class Run
 
 Public Shared Sub Main()
 Dim test As New Run()
 test.SerializeObject("Override.xml")
 test.DeserializeObject("Override.xml")
 End Sub 
 
 Public Sub SerializeObject(ByVal filename As String)
 ' Each overridden field, property, or type requires
 ' an XmlAttributes object. 
 Dim attrs As New XmlAttributes()
 
 ' Create an XmlElementAttribute to override the
 ' field that returns Instrument objects. The overridden field
 ' returns Brass objects instead. 
 Dim attr As New XmlElementAttribute()
 attr.ElementName = "Brass"
 attr.Type = GetType(Brass)
 
 ' Add the element to the collection of elements.
 attrs.XmlElements.Add(attr)
 
 ' Create the XmlAttributeOverrides object.
 Dim attrOverrides As 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(GetType(Orchestra), "Instruments", attrs)
 
 ' Create the XmlSerializer using the XmlAttributeOverrides.
 Dim s As New XmlSerializer(GetType(Orchestra), attrOverrides)
 
 ' Writing the file requires a TextWriter.
 Dim writer As New StreamWriter(filename)
 
 ' Create the object that will be serialized.
 Dim band As New Orchestra()
 
 ' Create an object of the derived type.
 Dim i As New Brass()
 i.Name = "Trumpet"
 i.IsValved = True
 Dim myInstruments() As Instrument = {i}
 band.Instruments = myInstruments
 
 ' Serialize the object.
 s.Serialize(writer, band)
 writer.Close()
 End Sub
 
 
 Public Sub DeserializeObject(ByVal filename As String)
 Dim attrOverrides As New XmlAttributeOverrides()
 Dim attrs As New XmlAttributes()
 
 ' Create an XmlElementAttribute to override the Instrument.
 Dim attr As New XmlElementAttribute()
 attr.ElementName = "Brass"
 attr.Type = GetType(Brass)
 
 ' Add the element to the collection of elements.
 attrs.XmlElements.Add(attr)
 
 attrOverrides.Add(GetType(Orchestra), "Instruments", attrs)
 
 ' Create the XmlSerializer using the XmlAttributeOverrides.
 Dim s As New XmlSerializer(GetType(Orchestra), attrOverrides)
 
 Dim fs As New FileStream(filename, FileMode.Open)
 Dim band As Orchestra = CType(s.Deserialize(fs), Orchestra)
 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. 
 Dim b As Brass
 Dim i As Instrument
 For Each i In band.Instruments
 b = CType(i, Brass)
 Console.WriteLine(b.Name + ControlChars.Cr + _
 b.IsValved.ToString())
 Next i
 End Sub
End Class

Remarks

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 that 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.

See also

• XmlAttributeOverrides
• XmlSerializer
• Introducing XML Serialization
• How to: Specify an Alternate Element Name for an XML Stream
• Controlling XML Serialization Using Attributes
• Examples of XML Serialization
• XML Schema Definition Tool (Xsd.exe)