C#Action和Func参数重载

public delegate void Action();
public delegate void Action<in T>(T obj);
public delegate void Action<in T1, in T2>(T1 arg1, T2 arg2);
// ...

public delegate TResult Func<out TResult>();
public delegate TResult Func<in T, out TResult>(T arg);
public delegate TResult Func<in T1, in T2, out TResult>(T1 arg1, T2 arg2);
// ...

public static void PrintMessage()
{
    Console.WriteLine("Hello, World!");
}

public static void PrintMessage(string message)
{
    Console.WriteLine(message);
}

public static int AddNumbers(int a, int b)
{
    return a + b;
}

Action printAction = PrintMessage;
printAction();  // 输出：Hello, World!

Action<string> printActionWithMessage = PrintMessage;
printActionWithMessage("Welcome!");  // 输出：Welcome!

Func<int, int, int> addFunc = AddNumbers;
int result = addFunc(2, 3);  // result的值为5