在.NET 2.0 C＃扩展方法 [英] C# Extension methods in .NET 2.0

问题描述

我已经发现了几个链接，这使得扩展方式方法的工作.NET2.0（的飞蛾，的不和谐和放大器;韵，堆栈溢出）。我也听到隐约从一个同事，这会导致一些问题库什么的？这样的话？此外，各3使用不同的方法：

I have found several links to methods of making extension methods work in .NET2.0 (The moth, Discord & Rhyme, Stack Overflow). I have also heard vaguely from a colleague that this causes some problems with libraries or something? Is this the case? Also all 3 use different methods:

飞蛾

namespace System.Runtime.CompilerServices
{
  public class ExtensionAttribute : Attribute { }
}

龃龉和韵

namespace System.Runtime.CompilerServices
{
  [AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = false)]
  public class ExtensionAttribute : Attribute {}
}

堆栈溢出

namespace System.Runtime.CompilerServices
{
    [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Class
         | AttributeTargets.Method)]
    public sealed class ExtensionAttribute : Attribute {}
}

请告诉我这些方法之间的区别，以及哪一个，你会推荐？

Whats the difference between these methods, and which one would you recommend?

推荐答案

归根结底，是不会太大的差别;你可能会说，一个运行期匹配是preferred，但是的理想的答案是，在以后的日子就可以使用不同版本的同一个容易混淆，否则切换到.NET 3.5（属性范围等）。

Ultimately it isn't going to make much difference; you could argue that the one that matches the runtime is preferred, but the ideal answer is to switch to .NET 3.5 (otherwise at a later date it can get confusing with different versions of the same attribute in scope etc).

在 [AttributeUsage] 将prevent它被连接到的东西，它不会做任何事情 - 但它不会做aything的本身的反正...

The [AttributeUsage] will prevent it being attached to things where it won't do anything - but it won't do aything by itself anyway...

看着对元数据类型，确切属性的使用似乎是最喜欢的计算器变种 - 但最终，这不是非常重要的 - 在名称和命名空间的是所有该事项（并且是由属性继承）。

Looking at metadata against the type, the exact attribute usage seems most like the stackoverflow variant - but ultimately this isn't hugely important - the name and namespace is all that matters (and that it inherits from Attribute).

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