C#委托delegate

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using static System.Console;
using static System.Convert;

namespace firstCsharp
{
    class Program
    {
        delegate double processdelegate(double param1, double param2);
        static double Multiply(double param1, double param2) => param1 * param2;
        static double Divide(double param1, double parma2) => param1 / parma2;

        static void Main(string[] args)
        {
            processdelegate process=null;
            WriteLine("please enter two number ,seperator by ',' :");
            string input = ReadLine();
            int compos = input.IndexOf(',');
            double param1 = ToDouble(input.Substring(0, compos));
            double param2 = ToDouble(input.Substring(compos + 1));
            WriteLine("Enter M for Multiply,D for Divide.");
            input = ReadLine().ToUpper();
            if(input=="M")
            {
                process = new processdelegate(Multiply);
            }
            else if(input=="D")
            {
                process = new processdelegate(Divide);
            }
            WriteLine($"result: {process(param1, param2)}");
            ReadKey();
        }
    }
}

processdelegata委托的声明要指定返回类型和参数类型。声明processdelegata变量process时要初始化，这里设为null。

调用相应的函数使用process=new processdelegata（函数名），然后直接调用process。