整理几种委托的用法Action，Func，匿名，多播，Lambde表达式，event

1.常用委托形式：

例子：

              public static void Main (string[] args){Meet ("China");Meet ("Japan");}public static void SayHelloInChina(){Console.WriteLine ("吃了吗？");}public static void SayHelloInAmerica(){Console.WriteLine ("what is the weather?");}public static void SayHelloInJapan(){Console.WriteLine ("孔丽西瓦！");}public static void SayHelloInHanGuo(){Console.WriteLine ("……思密达");}public static void SayHelloInAnyCountry(){}public static void Meet(string s){if (s == "China") {SayHelloInChina ();}if (s == "America" ) {SayHelloInAmerica ();}if (s == "Japan") {SayHelloInJapan ();}if (s == "HanGuo") {SayHelloInHanGuo ();}}

应用委托：

          public static void Main (string[] args){//通过委托去执行方法//委托的本质就是将方法作为参数进行引用Meet(SayHelloInChina);//直接把需要执行的方法名字传进来，委托会自动匹配Meet (SayHelloInHanGuo);}public static void SayHelloInChina(){Console.WriteLine ("吃了吗？");}public static void SayHelloInAmerica(){Console.WriteLine ("what is the weather?");}public static void SayHelloInJapan(){Console.WriteLine ("孔丽西瓦！");}public static void SayHelloInHanGuo(){Console.WriteLine ("……思密达");}public static void SayHelloInAnyCountry(){}public static void Meet (SayHello say)//把委托传进来{say ();//去执行这个委托}

2.委托形式二

        public delegate void kid();//声明一个小弟的委托class MainClass{public static void Main (string[] args){//实例化大哥类Boss boss = new Boss ();//给委托添加委托的方法kid kid = new kid (boss.Robe);kid += boss.Kill;//委托链，kid += boss.Fire;//消除委托的方法kid -= boss.Kill;kid -= boss.Fire;kid -= boss.Robe;//一般委托会这么用，不然委托里面委托的事件为空的话，会出现空引用的警告if (kid != null) {kid ();//执行委托}}}//定义大哥类public class Boss{public void Fire(){Console.WriteLine ("放火……");}public void Kill(){Console.WriteLine ("砍他……");}public void Robe(){Console.WriteLine ("抢劫了，把钱交粗来……");}}

3.带参数的委托

        /// <summary>/// 计算器的委托/// </summary>public delegate double DlgtCounter (float a,float b);class MainClass{public static void Main (string[] args){Count ct = new Count ();//DlgtCounter dcer = new DlgtCounter(ct.Add);Accountant ac = new Accountant ();//Console.WriteLine (ac.Operation (dcer, 4f, 5f));Console.WriteLine (ac.Operation (ct.Add, 3f, 5f));Console.WriteLine (ac.Operation (ct.Sub, 3f, 5f));Console.WriteLine (ac.Operation (ct.Mul, 3f, 5f));Console.WriteLine (ac.Operation (ct.Divide, 3f, 5f));}}/// <summary>/// 会计类，里面有操作的方法/// </summary>public class Accountant{//利用计算器（委托）去计算public double Operation(DlgtCounter counter,float a, float b){return counter (a, b);}}/// <summary>/// 计算类，里面有加减乘除的方fgfcr0法/// </summary>public class Count{public double Add(float a,float b){return a + b;}public double Sub(float a,float b){return a - b;}public double Mul(float a,float b){return a * b;}public double Divide(float a,float b){return a / b;}}

4.Action

             public static void Main (string[] args){//Action可以通过泛型去指定Action指向的方法的多个参数类型//参数的类型必须要与Action声明时后面的参数一致（顺序也不能错）Action a = PrintHelloWorld;a ();Action<string> b = PrintString;b ("shenmoyisi");Action<int,int> c = PrintDoubleInt;c (2, 4);Action<int,int,string, bool> d = Print;d (1, 2, "干什么", false);}public static void PrintHelloWorld(){Console.WriteLine ("Hello World.");}public static void PrintString(string str){Console.WriteLine (str);}public static void PrintDoubleInt(int a, int b){Console.WriteLine (a+ " "+ b);}public static void Print(int a, int b, string c, bool d){Console.WriteLine (a+ " " + b+ " " +c+ " " + d);}

5.Func

//Func 代表具有返回值的委托,//Func中可以跟很多类型，<>中前面的都是参数类型，最后一个是返回值类型//参数类型必须跟指定方法的参数一致，有0~16个参数class MainClass{public static void Main (string[] args){Func<int> a = Test01;Console.WriteLine (a ());Func<string , int> b = Test02;Console.WriteLine (b ("干什么"));Func<int,int,int> c = Test03;int res = c (12,45);Console.WriteLine (res);}public static int Test01(){return 1;}public static int Test02(string str){return 2;}public static int Test03(int a,int b){return a + b;}}

6.多播委托

class MainClass{public static void Main (string[] args){Action a = Test01;a += Test02;//a -= Test01;//消除方法//a -= Test02;if (a != null) {a ();}//当一个委托，没有指向任何一个方法的时候调用会出现空引用异常//如果方法有返回值，那么多播委托（委托链）只能得到最后一个方法的返回值//一般我们会把多播委托，的返回值定义成void//多播委托是一个逐个调用的委托集合//如果通过委托调用的任何一个方法出现的异常，整个迭代就会停止。//定义一个委托集合。 得到多播委托里面所有的单个委托Delegate[] dlgts = a.GetInvocationList();//遍历所有委托foreach (Delegate i in dlgts) {//执行委托i.DynamicInvoke ();}}public static void Test01(){Console.WriteLine ("Test01");//throw new Exception ();//抛出一个异常，执行不了，也就是说，委托连，中有一个异常就会执行不了}public static void Test02(){Console.WriteLine ("Test02");}}

7.匿名委托

class MainClass{public static int Plus(int a,int b){return a + b;}public static void Main (string[] args){//不使用匿名方法Func<int,int,int> f1 = Plus;int res1 = f1(12, 34);Console.WriteLine ("通过f1得到： "+res1);//使用匿名方法,本质上是一个方法，只是没有名字，也不需要写返回值//任何使用委托方法的地方都能使用匿名方法进行赋值Func<int,int,int> f2 = delegate (int a, int b) {return a + b;};int res2 = f2 (23, 45);Console.WriteLine ("通过f2得到： " +res2);Func<int,int,int> f3 = delegate(int a, int b) {return a - b;};int qwe = f3(4,2);}}

8.Lambda表达式

public static void Main (string[] args){//匿名方法Func<int,int,int> f2 = delegate (int a, int b) {return a + b;};//Lambda表达式,用来代替匿名方法，所以表达式中也定义一个方法//Lambda表达式中的参数是可以不声明类型的Func<int,int,int> f3 = (arg1, arg2) => {return arg1 + arg2;};//Func<int,int,int>f3 = (arg1, arg2) => arg1 + arg2;Console.WriteLine (f3(12,12));//Lambda表达式中只有一个参数的时候可以不加小括号//当函数的语句只有一句的时候，可以不加大括号和return；//如果说多条语句的会必须加Func<int,int>f4 = arg => 456;Console.WriteLine ("f4: " + f4(123));//任何使用委托方法的地方都能使用匿名方法进行赋值//只要有匿名方法的地方就能使用Lambda表达式//Lambda表达式,可以用来代替匿名方法Func<int,int> f5 = arg => ++arg;Console.WriteLine ("f5 : " + f5(13));Func <string,int> f6 = asdf => 1234;int azxc = f6 ("干什么");}}

9.event

public delegate void MyDelegate();class MainClass{//声明一个委托类型的变量//public MyDelegate myDelegate;//声明一个事件，该怎么用怎么用，没有什么改变，public event MyDelegate myDelegate;public static void Main (string[] args){MainClass mc = new MainClass ();mc.myDelegate = Test;mc.myDelegate ();}public static void Test(){Console.WriteLine ("Test");}}public delegate void MyDelegete();class Test01{public event MyDelegate MyDelegete01;public static void Main01(string[] args01){Test01 t01 = new Test01 ();t01.MyDelegete01 = Test02;t01.MyDelegete01 ();}public static void Test02(){Console.WriteLine ("干什么");}}