如何在 C# 中进行静态转换? [英] How to do a static cast in C#?

问题描述

给定几个这样的类型:

interface I {}
class C : I {}

如何进行静态类型转换?我的意思是:如何以在编译时检查的方式更改其类型?

How can I do a static type cast? By this I mean: how can I change its type in a way that gets checked at compile time?

在 C++ 中，您可以执行 static_cast<I*>(c).在 C# 中，我能做的最好的事情就是创建一个备用类型的临时变量并尝试分配它:

In C++ you can do static_cast<I*>(c). In C# the best I can do is create a temporary variable of the alternate type and try to assign it:

var c = new C();
I i = c;  // statically checked

但这会妨碍流畅的编程.我必须创建一个新变量来进行类型检查.所以我决定了这样的事情:

But this prevents fluent programming. I have to create a new variable just to do the type check. So I've settled on something like this:

class C : I
{
    public I I { get { return this; } }
}

现在我可以通过调用 c.I 将 C 静态转换为 I.

Now I can statically convert C to I by just calling c.I.

在 C# 中有没有更好的方法来做到这一点?

Is there a better way to do this in C#?

(如果有人想知道我为什么要这样做，那是因为我使用显式接口实现，并且从另一个成员函数中调用其中一个需要先转换为接口类型，否则编译器找不到方法.)

(In case anyone's wondering why I want to do this, it's because I use explicit interface implementations, and calling one of those from within another member function requires a cast to the interface type first, otherwise the compiler can't find the method.)

更新

我想出的另一个选项是对象扩展:

Another option I came up with is an object extension:

public static class ObjectExtensions
{
    [DebuggerStepThrough]
    public static T StaticTo<T>(this T o)
    {
        return o;
    }
}

所以 ((I)c).Doit() 也可以是 c.StaticTo().Doit().嗯......可能仍然会坚持简单的演员表.想我还是会发布这个其他选项.

So ((I)c).Doit() could also be c.StaticTo<I>().Doit(). Hmm...probably will still stick with the simple cast. Figured I'd post this other option anyway.

推荐答案

使用您在 UPDATE 中提到的技巧编写一个扩展方法:

Write an extension method that uses the trick you mentioned in your UPDATE:

public static class ObjectExtensions
{
    public static T StaticCast<T>(this T o) => o;
}

使用方法:

things.StaticCast<IEnumerable>().GetEnumerator();

如果 things 是，例如 IEnumerable