委托和事件

 

    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(Object sender, EventArgs e)
        {
            Heater heater = new Heater();
            Alarm alarm = new Alarm();

            //注册方法
            heater.Boiled += alarm.MakeAlert;
            //给匿名对象注册方法
            heater.Boiled += (new Alarm()).MakeAlert;
            heater.Boiled += new Heater.BoiledEventHandler(alarm.MakeAlert);
            //注册静态方法
            heater.Boiled += Display.ShowMsg;

            //烧水，自动调用注册过对象的方法
            heater.BoileWater();
        }
    }

    public class Heater {

        private int temperature;
        //添加型号作为演示
        public string type = "RealFire 001";
        //添加出产地作为演示
        public string area = "China Xian";
        //声明委托
        public delegate void BoiledEventHandler(Object sender, BoiledEventArgs e);
        //声明事件
        public event BoiledEventHandler Boiled;

        //定义BoiledEventArgs类，传递给Observer所感兴趣的信息
        public class BoiledEventArgs : EventArgs {

            public readonly int temperature;
            public BoiledEventArgs(int temperature) {
                this.temperature = temperature;
            }
        }
        //可以供继承自Heater的类重写，以便继承类拒绝其他对象对它的监视
        protected virtual void OnBoiled(BoiledEventArgs e) {
            //如果有对象注册，调用所有注册对象的方法
            if (Boiled != null)
                Boiled(this, e);
        }
        //烧水
        public void BoileWater() {
            for (int i = 0; i <= 100; i++) {
                temperature = i;
                if (temperature > 98) {
                    //建立BoiledEventArgs对象
                    BoiledEventArgs e = new BoiledEventArgs(temperature);
                    //调用OnBoiled方法
                    OnBoiled(e);
                }
            }
        }
    }

    //警报器
    public class Alarm {

        public void MakeAlert(Object sender, Heater.BoiledEventArgs e) {
            Heater heater = (Heater)sender;
            MessageBox.Show(string.Format("Alarm：{0}-{1}", heater.area, heater.type));
            MessageBox.Show(string.Format("Alarm：水已经{0}度了", e.temperature));
        }
    }

    //显示器
    public class Display {

        public static void ShowMsg(Object sender, Heater.BoiledEventArgs e) {
            Heater heater = (Heater)sender;
            //访问sender中的公共字段
            MessageBox.Show(string.Format("Display：{0}-{1}", heater.area, heater.type));
            MessageBox.Show(string.Format("Display：水快烧开了，当前{0}度", e.temperature));
        }
    }