在.NET 2.0中使用扩展方法？

I want to do this, but getting this error:

我想这样做，但得到这个错误：

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]

错误1无法定义新的扩展方法，因为无法找到编译器所需的类型“System.Runtime.CompilerServices.ExtensionAttribute”。您是否缺少对System.Core.dll的引用？ [剪断了一些路径]

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

我在这里看到一些答案，你必须自己定义这个属性。

How do I do that?

我怎么做？

EDIT: This is what I have:

编辑：这就是我所拥有的：

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

    }
}

1 个解决方案

#1

Like so:

像这样：

// 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.

另外;只需添加对LINQBridge的引用。

#1