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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)

'Declaration
Public Class XmlAttributes
'Usage
Dim instance As XmlAttributes

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
#using <mscorlib.dll>
#using <System.Xml.dll>
#using <System.dll>
using namespace System;
using namespace System::IO;
using namespace System::Xml::Serialization;

public __gc class Instrument
{
public:
   String* Name;
};

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

public __gc class Orchestra
{
public:
   Instrument* Instruments[];
};   

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 = S"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), S"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 = S"Trumpet";
   i->IsValved = true;
   Instrument* myInstruments[] = {i};
   band->Instruments = myInstruments;

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

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 = S"Brass";
   attr->Type = __typeof(Brass);

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

   attrOverrides->Add(__typeof(Orchestra), S"Instruments", attrs);

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

   FileStream* fs = new FileStream(filename, FileMode::Open);
   Orchestra* band = dynamic_cast<Orchestra*> (s->Deserialize(fs));
   Console::WriteLine(S"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 = __try_cast<Instrument*>(myEnum->Current);
      b = dynamic_cast<Brass*>(i);
      Console::WriteLine(
         S"{0}\n{1}", b->Name, __box(b->IsValved));
   }
}

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

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 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

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

.NET Framework

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

.NET Compact Framework

Supported in: 3.5, 2.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

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