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.NET Framework Class Library
ExtensionAttribute Class

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

Inheritance Hierarchy
SystemObject
   SystemAttribute
    System.Runtime.CompilerServicesExtensionAttribute

Namespace:   System.Runtime.CompilerServices
Assembly:  mscorlib (in mscorlib.dll)
Syntax
<[%$TOPIC/bb504090_en-us_VS_110_2_0_0_0_0%]([%$TOPIC/bb504090_en-us_VS_110_2_0_0_0_1%].Assembly Or [%$TOPIC/bb504090_en-us_VS_110_2_0_0_0_2%].Class Or [%$TOPIC/bb504090_en-us_VS_110_2_0_0_0_3%].Method)> _
Public NotInheritable Class ExtensionAttribute _
	Inherits [%$TOPIC/bb504090_en-us_VS_110_2_0_0_0_4%]
[[%$TOPIC/bb504090_en-us_VS_110_2_0_1_0_0%]([%$TOPIC/bb504090_en-us_VS_110_2_0_1_0_1%].Assembly|[%$TOPIC/bb504090_en-us_VS_110_2_0_1_0_2%].Class|[%$TOPIC/bb504090_en-us_VS_110_2_0_1_0_3%].Method)]
public sealed class ExtensionAttribute : [%$TOPIC/bb504090_en-us_VS_110_2_0_1_0_4%]
[[%$TOPIC/bb504090_en-us_VS_110_2_0_2_0_0%]([%$TOPIC/bb504090_en-us_VS_110_2_0_2_0_1%]::Assembly|[%$TOPIC/bb504090_en-us_VS_110_2_0_2_0_2%]::Class|[%$TOPIC/bb504090_en-us_VS_110_2_0_2_0_3%]::Method)]
public ref class ExtensionAttribute sealed : public [%$TOPIC/bb504090_en-us_VS_110_2_0_2_0_4%]
[<[%$TOPIC/bb504090_en-us_VS_110_2_0_3_0_0%]>]
[<[%$TOPIC/bb504090_en-us_VS_110_2_0_3_0_1%]([%$TOPIC/bb504090_en-us_VS_110_2_0_3_0_2%].Assembly|[%$TOPIC/bb504090_en-us_VS_110_2_0_3_0_3%].Class|[%$TOPIC/bb504090_en-us_VS_110_2_0_3_0_4%].Method)>]
type ExtensionAttribute =  
    class 
        inherit [%$TOPIC/bb504090_en-us_VS_110_2_0_3_0_5%] 
    end

The ExtensionAttribute type exposes the following members.

Constructors
  NameDescription
Public method Supported by the XNA Framework Supported by Portable Class Library Supported in .NET for Windows Store apps ExtensionAttributeInitializes a new instance of the ExtensionAttribute class.
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Properties
  NameDescription
Public property TypeIdWhen implemented in a derived class, gets a unique identifier for this Attribute. (Inherited from Attribute.)
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Methods
  NameDescription
Public method Supported by the XNA Framework Supported by Portable Class Library Supported in .NET for Windows Store apps EqualsInfrastructure. Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute.)
Public method Supported by the XNA Framework Supported by Portable Class Library Supported in .NET for Windows Store apps GetHashCodeReturns the hash code for this instance. (Inherited from Attribute.)
Public method Supported by the XNA Framework Supported by Portable Class Library Supported in .NET for Windows Store apps GetTypeGets the Type of the current instance. (Inherited from Object.)
Public method IsDefaultAttributeWhen 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 MatchWhen overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute.)
Public method Supported by the XNA Framework Supported by Portable Class Library Supported in .NET for Windows Store apps ToStringReturns a string that represents the current object. (Inherited from Object.)
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Explicit Interface Implementations
  NameDescription
Explicit interface implemetation Private method _AttributeGetIDsOfNamesMaps a set of names to a corresponding set of dispatch identifiers. (Inherited from Attribute.)
Explicit interface implemetation Private method _AttributeGetTypeInfoRetrieves 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 _AttributeGetTypeInfoCountRetrieves the number of type information interfaces that an object provides (either 0 or 1). (Inherited from Attribute.)
Explicit interface implemetation Private method _AttributeInvokeProvides 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

.NET for Windows Store apps

Supported in: Windows 8
Platforms

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.

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.