¿Utiliza métodos de extensión en .NET 2.0?

Question

quiero hacer esto, pero conseguir este error:

Error 1 Cannot define a new extension method because the compiler required type 'System.Runtime.CompilerServices.ExtensionAttribute' cannot be found. Are you missing a reference to System.Core.dll? [snipped some path stuff]

he visto algunas respuestas aquí que dice, usted tiene que definir este atributo a sí mismo.

Cómo lo hago?

EDITAR: Esto es lo que tengo:

[AttributeUsage (AttributeTargets.Assembly | AttributeTargets.Class | AttributeTargets.Method)] 
public sealed class ExtensionAttribute : Attribute 
{ 
    public static int MeasureDisplayStringWidth (this Graphics graphics, string text) 
    { 

    } 
} 

Answer 1

así:

// you need this once (only), and it must be in this namespace 
namespace System.Runtime.CompilerServices 
{ 
    [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Class 
     | AttributeTargets.Method)] 
    public sealed class ExtensionAttribute : Attribute {} 
} 
// you can have as many of these as you like, in any namespaces 
public static class MyExtensionMethods { 
    public static int MeasureDisplayStringWidth (
      this Graphics graphics, string text) 
    { 
      /* ... */ 
    } 
} 

alternativa; solo agregue una referencia a LINQBridge.