c# - 在这种情况下，为什么 C# 无法解析正确的重载？

Question

我遇到过一个很奇怪的情况，它是明确的，但重载解析器并不这么认为。考虑:

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!
    }
}

为什么对 ParamTest 重载的调用被正确解析，但是 Test 重载是不明确的？

Answer 1

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

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 的唯一区别在于返回值。

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

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.