为什么在这种情况下C＃无法解决正确的重载？ [英] Why cannot C# resolve the correct overload in this case?

问题描述

我遇到了一个很明确的奇怪情况，但是过载解析器却不这么认为。考虑：

I've come across a strange situation which is non-ambiguous, yet the overload resolver doesn't think so. Consider:

public static class Program
{
    delegate int IntDel();
    delegate string StringDel();

    delegate void ParamIntDel(int x);
    delegate void ParamStringDel(string x);

    static void Test(IntDel fun) { }
    static void Test(StringDel fun) { }
    static void ParamTest(ParamIntDel fun) { }
    static void ParamTest(ParamStringDel fun) { }

    static int X() { return 42; }
    static void PX(int x) { }

    public static void Main(string[] args)
    {
        ParamTest(PX); // OK
        Test(X); // Ambiguos call!
    }
}

如何呼叫 ParamTest 重载可以正确解决，但是 Test 重载是模棱两可的？

How come the call to ParamTest overloads is resolved correctly, but Test overload is ambiguous?

推荐答案

也许是因为 https： //msdn.microsoft.com/zh-CN/library/aa691131%28v=vs.71%29.aspx

方法的签名明确地不包括返回类型，也不包括可能为最右边的参数指定的params修饰符。

The signature of a method specifically does not include the return type, nor does it include the params modifier that may be specified for the right-most parameter.

IntDel 和 StringDel 之间的唯一区别是返回值。

And the only difference between IntDel and StringDel is in the return value.

更具体地说： https：// msdn。 microsoft.com/en-us/library/ms173171.aspx

在方法重载的情况下，方法的签名不包含返回值。但是在委托的上下文中，签名确实包含返回值。换句话说，方法的返回类型必须与委托相同。

In the context of method overloading, the signature of a method does not include the return value. But in the context of delegates, the signature does include the return value. In other words, a method must have the same return type as the delegate.

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