ExtensionAttribute Class (System.Runtime.CompilerServices)

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.NET Framework Class Library
ExtensionAttribute Class

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Indicates that a method is an extension method, or that a class or assembly contains extension methods.

Inheritance Hierarchy
System.Object
  System.Attribute
    System.Runtime.CompilerServices.ExtensionAttribute

Namespace:  System.Runtime.CompilerServices
Assembly:  mscorlib (in mscorlib.dll)
Syntax
Visual Basic
<AttributeUsageAttribute(AttributeTargets.Assembly Or AttributeTargets.Class Or AttributeTargets.Method)> _
Public NotInheritable Class ExtensionAttribute _
	Inherits Attribute
C#
[AttributeUsageAttribute(AttributeTargets.Assembly|AttributeTargets.Class|AttributeTargets.Method)]
public sealed class ExtensionAttribute : Attribute
Visual C++
[AttributeUsageAttribute(AttributeTargets::Assembly|AttributeTargets::Class|AttributeTargets::Method)]
public ref class ExtensionAttribute sealed : public Attribute
F#
[<Sealed>]
[<AttributeUsageAttribute(AttributeTargets.Assembly|AttributeTargets.Class|AttributeTargets.Method)>]
type ExtensionAttribute =  
    class
        inherit Attribute
    end

The ExtensionAttribute type exposes the following members.

Constructors
  Name Description
Public method Supported by the XNA Framework Supported by Portable Class Library ExtensionAttribute Initializes a new instance of the ExtensionAttribute class.
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Properties
  Name Description
Public property TypeId When implemented in a derived class, gets a unique identifier for this Attribute. (Inherited from Attribute.)
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Methods
  Name Description
Public method Supported by the XNA Framework Supported by Portable Class Library Equals Infrastructure. Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute.)
Protected method Supported by the XNA Framework Supported by Portable Class Library Finalize Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public method Supported by the XNA Framework Supported by Portable Class Library GetHashCode Returns the hash code for this instance. (Inherited from Attribute.)
Public method Supported by the XNA Framework Supported by Portable Class Library GetType Gets the Type of the current instance. (Inherited from Object.)
Public method IsDefaultAttribute When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class. (Inherited from Attribute.)
Public method Supported by the XNA Framework Match When overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute.)
Protected method Supported by the XNA Framework Supported by Portable Class Library MemberwiseClone Creates a shallow copy of the current Object. (Inherited from Object.)
Public method Supported by the XNA Framework Supported by Portable Class Library ToString Returns a string that represents the current object. (Inherited from Object.)
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Explicit Interface Implementations
  Name Description
Explicit interface implemetation Private method _Attribute.GetIDsOfNames Maps a set of names to a corresponding set of dispatch identifiers. (Inherited from Attribute.)
Explicit interface implemetation Private method _Attribute.GetTypeInfo Retrieves the type information for an object, which can be used to get the type information for an interface. (Inherited from Attribute.)
Explicit interface implemetation Private method _Attribute.GetTypeInfoCount Retrieves the number of type information interfaces that an object provides (either 0 or 1). (Inherited from Attribute.)
Explicit interface implemetation Private method _Attribute.Invoke Provides access to properties and methods exposed by an object. (Inherited from Attribute.)
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Remarks

In Visual Basic, you should use this attribute to create an extension method. For more information, see Extension Methods (Visual Basic).

In C#, you do not need to use this attribute; you should use the this (C# Reference) modifier for the first parameter to create an extension method. The compiler automatically emits ExtensionAttribute for extension methods. For more information, see Extension Methods (C# Programming Guide).

If you are writing a compiler that supports extension methods, your compiler should emit this attribute on each extension method and on each class and assembly that contains one or more extension methods.

Version Information

.NET Framework

Supported in: 4.5, 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library
Platforms

Windows 8 Consumer Preview, Windows Server 8 Beta, Windows 7, Windows Server 2008 SP2, 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.

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

Reference

System.Runtime.CompilerServices Namespace

Other Resources

Extension Methods (Visual Basic)
Extension Methods (C# Programming Guide)