XmlAttributes Class
Assembly: System.Xml (in system.xml.dll)
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.
Imports System Imports System.IO Imports System.Xml.Serialization Imports Microsoft.VisualBasic 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
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
Windows 98, Windows 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 .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.
Reference
XmlAttributes MembersSystem.Xml.Serialization Namespace
XmlAttributeOverrides Class
XmlSerializer
XmlAttributes Class
Other Resources
Introducing XML SerializationHow 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)