编辑代码

using System;
public class HelloWorld
{
    public static void Main()
    {
        Caculator c = new Caculator();
        Action action = new Action(c.Report);
        c.Report();
        action.Invoke();
        action();

        Func<int,int,int> func1 = new Func<int,int,int>(c.Add); 
        Func<int,int,int> func2 = new Func<int,int,int>(c.Sub); 
        int x =100;
        int y =200;
        int z =0;

        z = func1(x,y);
        Console.WriteLine(z);
        z = func2(x,y);
        Console.WriteLine(z);
        
    }
}

class Caculator
{
    public void Report()
    {
        Console.WriteLine("I have 3 methods.");
    }

    public int Add(int a,int b)
    {
        int result = a+b;
        return result;
    }
    public int Sub(int a,int b)
    {
        int result = a-b;
        return result;
    }
}