C#Polymorphysm：重载函数,接受委托Action和Func？

您可以看到重载的Invoker函数,接受Func< T,R>和动作< T>作为一个论点.

如果使用Invoker方法,编译器说由于模糊不清而无法编译：

class Program
{
    static void Invoker(Action<XDocument> parser)
    {
    }

    static void Invoker(Func<XDocument,string> parser)
    {
    }

    static void Main(string[] args)
    {
        Invoker(Action);
        Invoker(Function);
    }

    static void Action(XDocument x)
    {
    }

    static string Function(XDocument x)
    {
        return "";
    }
}

我得到3(！)错误,但我无法解释.他们来了：

Error 1 The call is ambiguous between the following methods or properties: ‘ConsoleApplication3.Program.Invoker(System.Action)’ and ‘ConsoleApplication3.Program.Invoker(System.Func)’ c:usersi.smagindocumentsvisual studio 2010ProjectsConsoleApplication3ConsoleApplication3Program.cs 21 4 ConsoleApplication3

Error 2 The call is ambiguous between the following methods or properties: ‘ConsoleApplication3.Program.Invoker(System.Action)’ and ‘ConsoleApplication3.Program.Invoker(System.Func)’ c:usersi.smagindocumentsvisual studio 2010ProjectsConsoleApplication3ConsoleApplication3Program.cs 22 4 ConsoleApplication3

Error 3 ‘string ConsoleApplication3.Program.Function(System.Xml.Linq.XDocument)’ has the wrong return type c:usersi.smagindocumentsvisual studio 2010ProjectsConsoleApplication3ConsoleApplication3Program.cs 22 12 ConsoleApplication3

有任何想法吗？