C# 委托和方法

委托是一种特殊的引用类型，它将方法也作为特殊的对象封装起来，从而将方法作为变量或参数进行传递

 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;

 namespace ConsoleApplication1
 {
     delegate void DualFunction(double x,double y);
     class Program
     {
         static void Main()
         {
             DualFunction fun1;
             double a = 2.5, b = ;
             Console.WriteLine("请选择函数（加0减1乘2除3）:");
             int i = int.Parse(Console.ReadLine());
             if (i == )
                 fun1 = new DualFunction(Sub);
             else if (i == )
                 fun1 = new DualFunction(Mul);
             else if (i == )
                 fun1 = new DualFunction(Div);
             else
                 fun1 = new DualFunction(Add);
             fun1(a, b);
             Console.ReadLine();
         }
         static void Add(double x,double y)
         {
             Console.WriteLine("{0}+{1}={2}", x, y, x + y);
         }
         static void Sub(double x,double y)
         {
             Console.WriteLine("{0}-{1}={2}", x, y, x - y);
         }
         static void Mul(double x,double y)
         {
             Console.WriteLine("{0}*{1}={2}", x, y, x * y);
         }
         static void Div(double x,double y)
         {
             Console.WriteLine("{0}/{1}={2}", x, y, x / y);
         }
     }
 }

DaulFunction fun1=new DualFunction(Sub);

DualFunction fun1=Sub;//这两种方式也行

还可以将委托对象放在数组中  比如

static void Main()
{
DualFunction[] funs = new DualFunction[] { Add, Sub, Mul, Div };
double a=2.5, b=2.0;
Console.WriteLine("请选择函数（加0减1乘2除3）：");
int i = int.Parse(Console.ReadLine());
funs[i](a, b);
Console.ReadLine();
}

一个委托对象还可以封装多个方法   委托对象的合并和删除  比如DualFunction fun1 = funs[1] + funs[2];