委托 事件

1.定义委托  : 方法定义前 加 delegate 

public delegate void NoReturnNoPara();
public delegate void NoReturnWithPara(int x, int y);//1 声明委托
public delegate int WithReturnNoPara();
public delegate string WithReturnWithPara(out int x, ref int y);

2. 实例化委托   要求传入完全吻合的方法

 NoReturnNoPara method = new NoReturnNoPara(this.DoNothing)

private void DoNothing()
{
Console.WriteLine("This is DoNothing");
}

3.调用委托

NoReturnWithPara method = new NoReturnWithPara(this.DoNothingPara);

method.Invoke(1,2)

private void DoNothingPara(int x, int y)
{
Console.WriteLine("This is DoNothing");
}

4.泛型委托

Action act1 = () => { };
Action<int> act2 = i => { };//如果只有一个参数 可以去掉小括号
Action<int, string, int, int, string, int, int, string, int, int, string, int, int, string, int, string> act17 = null

Func<int> fun1 = () => 123; //如果方法体只有一行,可以去掉大括号和分号 和return
Func<int, string> func2 = i => i.ToString();
Func<int, string, int, int, string, int, int, string, int, int, string, int, int, string, int, string, MyDelegate> fun17 = null;

5.多播委托

+= 表示向一个委托实例里面添加方法,形成方法链,invoke的时候,按添加顺序执行

Action act = new Action(this.DoNothing);
act += this.DoNothing;
act += DoNothingStatic;
act += other.DoNothing;
act += new OtherClass().DoNothing;
act += OtherClass.DoNothingStatic;
act += () => Console.WriteLine("这里是lambda表达式");
act.Invoke();

act.GetInvocationList().Length
act.BeginInvoke(null, null);//委托里面只能有一个方法
foreach (Action item in act.GetInvocationList())
 {
   item.BeginInvoke(null, null);
  }

-= 表示向一个委托实例里面移除方法,从方法链尾部开始匹配,遇到第一个完全吻合的,移除且只移除一个;没有匹配的,也不异常

act -= this.DoNothing;
act -= DoNothingStatic;
act -= other.DoNothing;
act -= new OtherClass().DoNothing; 
act -= OtherClass.DoNothingStatic;
act -= () => Console.WriteLine("这里是lambda表达式");
act.Invoke();

5.委托简化  ,lambda 表达式

1.   NoReturnWithPara method = new NoReturnWithPara(this.DoNothingPara);

2.NoReturnWithPara method = new NoReturnWithPara(delegate(int x, int y) {Console.WriteLine(iNum);Console.WriteLine("This is DoNothing");});

3.NoReturnWithPara method = new NoReturnWithPara((int x, int y) => //goes to  lambda表达式 本质是匿名方法 也就是个方法

{

Console.WriteLine(iNum);

Console.WriteLine("This is DoNothing");
 }

4.NoReturnWithPara method = new NoReturnWithPara((x, y) =>

// /参数类型可以去掉,因为约束的限制
{
 Console.WriteLine("This is DoNothing");
});

5.NoReturnWithPara method = new NoReturnWithPara((x, y) =>

 //如果方法体只有一行,可以去掉大括号和分号
 Console.WriteLine("This is DoNothing")
 );

6. NoReturnWithPara method = (x, y) => Console.WriteLine("This is DoNothing");

6. 事件

public event Action MiaoEventHandlerEvent;    在外部赋值   在内部调用
//事件就是委托的实例,增加event关键字,防止外部直接invoke和赋值
//事件和委托的区别联系?
//事件就是委托的实例,委托是一个类型 而事件是委托类型的一个实例
//Student是一个类型 而大山是Student类型的一个实例
public void MiaoActionEvent()
{
Console.WriteLine("{0} MiaoActionEvent", this.GetType().Name);

if (this.MiaoEventHandlerEvent != null)
 {
  this.MiaoEventHandlerEvent.Invoke();//子类都没办法invoke
 }
}

posted @ 2019-10-17 16:18  称虚圆  阅读(141)  评论(0编辑  收藏  举报