事件和委托

时间：2014-11-20 15:11:22 阅读：232 评论：0 收藏：0 [点我收藏+]

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委托：可以理解成为是装方法的容器委托是指向函数的指针

委托的定义: public delegate void SayHi();

delegate :定义委托的关键字 void 无返回值的委托（传入的方法是无返回值的） SayHi() : SayHi是委托名 ()表示传入的方法也是不带参数的

namespace DelegteAndEvent
{
    /// <summary>
    /// 定义委托
    /// </summary>
    /// <returns></returns>
    public  delegate void   SayHi();


   public class People
    {
       //定义事件
       public event SayHi SayHiByPeople;

       /// <summary>
       /// 事件的调用
       /// </summary>
       public void SayHiByPeopleDiaoYong()
       {
           this.SayHiByPeople();   //事件是属于对象的  在外部只能进行+=  或者-=  无法调用事件的  所在在内部调用
       }
   
       //委托变量
       public SayHi sayHi;

        public  void  SayHiByChinese()
        {
            Console.WriteLine("你好，我是中国人");
        }

        public void SayHiByEnglish()
        {
             
             Console.WriteLine("你好，我是英国人");
        }

        public void SayHiByJapanese()
        {
            Console.WriteLine("你好，我是日本人"); 
        }
       
    }
}

下面是窗体的界面

bubuko.com,布布扣

下面是为按钮添加的点击事件

  public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
       
        /// <summary>
        /// 委托的简单实用
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Delegtes_Click(object sender, EventArgs e)
        {
            People people = new People();

            people.sayHi = new SayHi(people.SayHiByChinese);

            //往委托链上挂载方法
            people.sayHi += people.SayHiByEnglish;
                      
            people.sayHi += people.SayHiByJapanese;

            //委托的执行
            people.sayHi();
     }




        /// <summary>
        /// 事件的简单使用
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Events_Click(object sender, EventArgs e)
        {

            People people = new People();
            //往事件尚挂载方法
            people.SayHiByPeople += people.SayHiByChinese;
            people.SayHiByPeople += people.SayHiByEnglish;          
            people.SayHiByPeople += people.SayHiByJapanese;
            //调用事件
            people.SayHiByPeopleDiaoYong();
        }



        /// <summary>
        /// 委托干扰
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void DelegtesGsnRao_Click(object sender, EventArgs e)
        {

            People people = new People();

            people.sayHi = new SayHi(people.SayHiByChinese);

            //往委托链上挂载方法
            people.sayHi += people.SayHiByEnglish;

            //如果为委托赋值为null   那么之前赋值的函数的指针将全部清空    这时只执行最后一个方法
            people.sayHi = null;

            people.sayHi += people.SayHiByJapanese;
            people.sayHi();
        }



        /// <summary>
        /// 事件和委托
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>

        private void DelgetAndEvenet_Click(object sender, EventArgs e)
        {
            People people = new People();
            //往事件尚挂载方法
            people.SayHiByPeople += people.SayHiByChinese;
            people.SayHiByPeople += people.SayHiByEnglish;
            people.SayHiByPeople = null;//这种做法是错的 事件在外部是不可以使用=进行赋值的
            people.SayHiByPeople += people.SayHiByJapanese;
            //调用事件
            people.SayHiByPeopleDiaoYong();
        }

      


    }