扩展方法和静态方法有什么区别？ [英] What is difference between extension method and static method?

问题描述

扩展方法和静态方法有什么区别？

What is the difference between an extension method and a static method ?

我有两个这样的类：

public static class AClass {
    public static int AMethod(string ....)
    {
    }
}

和

public static class BClass {
    public static int BMethod(this string ....)
    {
    }
}

我可以这样使用

AClass.AMethod('...');

或

'...'.BMethod();

建议哪个？

推荐答案

扩展方法仍然是静态方法。您可以像使用普通的静态方法一样使用它。

An extension method is still a static method. You can use it exactly as you'd use a normal static method.

唯一的区别是扩展方法允许您以类似于它是该类型的一部分，因此您可以编写：

The only difference is that an extension method allows you to use the method in a way that looks like it's part of the type, so you can write:

int result = stringValue.BMethod();

而不是：

int result = BClass.BMethod(stringValue);

这纯粹是作为编译技巧工作的-编译器会看到第一种形式，如果 BClass 是可用的（它具有正确的使用并且在引用的程序集中），然后将其转换为第二个方法适合您。纯粹是为了方便。

This works purely as a compile "trick" - the compiler sees the first form, and if the BClass is usable (it has a proper using and is in a referenced assembly), then it will turn it into the second method's IL for you. It's purely a convenience.

有人建议？

Which is proposed ?

这确实取决于。如果您控制类型，建议您将方法放在类型本身上。通常，这种方法更易于维护。

This really depends. If you control the type, I'd recommend putting the methods on the type itself. This is typically more maintainable.

如果您不控制类型，或者尝试扩展普通类型（例如 IEnumerable< T> ），那么扩展方法可能是一种合理的方法。

If you don't control the type, or you're trying to "extend" a common type (such as IEnumerable<T>), then extension methods may be a reasonable approach.

但是，如果类型是非常普通的类型，我通常会避免扩展方法，因为它们在智能感知中会变成噪音，从而可能引起额外的混乱。例如，我个人不建议在 System.Object 或 System.String 等上添加扩展方法。

However, if the type is a very common type, I'd typically avoid extension methods, as they become "noise" in intellisense, which in turn can cause extra confusion. For example, I would personally not recommend adding extension methods on System.Object or System.String, etc.

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