Using extension methods in .NET 2.0?

Question

I want to do this, but getting this 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]

I have seen some answers here that says, you have to define this attribute yourself.

How do I do that?

EDIT: This is what I have:

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

Answer 1

Like so:

// 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 )     {            /* ... */     } } 

Alternatively; just add a reference to LINQBridge.