如何在 C# 中基于现有委托类型创建新委托类型？
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How do I create a new delegate type based on an existing one, in C#?
提问by Shalom Craimer
Is there any way that I can create a new delegate type based on an existing one? In my case, I'd like to create a delegate MyMouseEventDelegatewhich would have the same functionality as EventHandler<MouseEventArgs>.
有什么方法可以基于现有的委托类型创建新的委托类型？就我而言，我想创建一个MyMouseEventDelegate与EventHandler<MouseEventArgs>.
Why do I want this? To take advantage of compile-time type-checking, of course! This way, I can have two different delegates: MyRightClickHandlerand MyLeftClickHandler, and never the twain shall be confused - even if they are both functionally identical to EventHandler<MouseEventArgs>.
我为什么要这个？当然，要利用编译时类型检查！这样，我可以有两个不同的代表：MyRightClickHandlerand MyLeftClickHandler，并且永远不会混淆两个代表- 即使它们在功能上都与EventHandler<MouseEventArgs>.
Is there syntax to do this sort of thing?
有没有语法来做这种事情？
Oh, and code like:
哦，代码如下：
using MyRightClickHandler = EventHandler<MouseEventArgs>
isn't good enough. It doesn't do any type-checking, since it doesn't actually create a new type. And I'd have to paste such a line into every code file in which I would refer to MyRightClickHandler.
不够好。它不做任何类型检查，因为它实际上并没有创建一个新类型。而且我必须将这样的一行粘贴到我要引用的每个代码文件中MyRightClickHandler。
采纳答案by Jon Skeet
Well, it's as simple as copying the delegate declaration from the original. There's nothing in C# to do this automatically, but I can't see it's much of a burden:
嗯，这就像从原始副本中复制委托声明一样简单。C# 中没有什么可以自动执行此操作，但我看不出它有多大负担：
public delegate void MyLeftClickHandler(object sender, MouseEventArgs e);
public delegate void MyRightClickHandler(object sender, MouseEventArgs e);
It's not like MouseEventHandleris going to change any time soon...
它不会MouseEventHandler很快改变......
Have you actually been bitten by bugs due to using the wrong delegates in the wrong places though? I can't remember ever having found this a problem myself, and it seems to me you're introducing more work (and an unfamiliar set of delegates for other developers) - are you sure it's worth it?
你是否真的因为在错误的地方使用错误的代表而被错误咬伤？我不记得自己曾经发现过这个问题，而且在我看来你正在引入更多的工作（以及其他开发人员不熟悉的一组委托） - 你确定它值得吗？
回答by Fredrik M?rk
I you only want to achieve compile time type checking I guess it would be enough to create specialized EventArgs classes for the cases that you describe. That way you can still take advantage of the pre-defined delegates:
我只想实现编译时类型检查，我想为您描述的情况创建专门的 EventArgs 类就足够了。这样你仍然可以利用预定义的委托：
class RightMouseButtonEventArgs : MouseEventArgs {}
class LeftMouseButtonEventArgs : MouseEventArgs {}
EventHandler<RightMouseButtonEventArgs>
EventHandler<LeftMouseButtonEventArgs>
回答by Oneironaut
No. According to the C# documentation, delegate types are sealed, and you cannot create a new delegate type that inherits from an existing one.
不可以。根据C# 文档，委托类型是密封的，您不能创建从现有委托类型继承的新委托类型。
回答by Trade-Ideas Philip
I didn't believe jon-skeet. I had to try it for myself. He was right.
我不相信乔恩斯基特。我不得不亲自尝试一下。他是对的。
public void F(object sender, MouseEventArgs e) {};
public MyLeftClickHandler l;
public MyRightClickHandler r;
public void Test()
{
l = F; // Automatically converted.
r = F; // Automatically converted to a different type.
l = r; // Syntax error. Incompatible types.
l = new MyLeftClickHandler(r); // Explicit conversion works.
}
That wasn't obvious!
那不是很明显！
