事件和委托

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2024-08-03 08:54:13 222人阅读

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

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();        }          }