事件委托

using System;
using System.Collections.Generic;
using System.Text;

namespace Delegate {
 // 热水器
 public class Heater {
  private int temperature;
  public string type = "RealFire 001";  // 添加型号作为演示
  public string area = "China Xian";   // 添加产地作为演示

  public delegate void BoiledEventHandler(Object sender, BoiledEventArgs e); //声明委托
  public event BoiledEventHandler Boiled; //声明事件

  // 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 OnBolied(BoiledEventArgs e) {
   if (Boiled != null) { //如果有对象注册
    Boiled(this, e);  //调用所有注册对象的方法
   }
  }
  
  // 烧水。
  public void BoilWater() {
   for (int i = 0; i <= 100; i++) {
    temperature = i;
    if (temperature > 95) {
     BoiledEventArgs e = new BoiledEventArgs(temperature);
     OnBolied(e);
    }
   }
  }
 }

 // 警报器
 public class Alarm {
  public void MakeAlert(Object sender, Heater.BoiledEventArgs e) {
   Heater heater = (Heater)sender;  //这里是不是很熟悉呢？
   //访问 sender 中的公共字段
   Console.WriteLine("Alarm：{0} - {1}: ", heater.area, heater.type);
   Console.WriteLine("Alarm: 嘀嘀嘀，水已经 {0} 度了：", e.temperature);
   Console.WriteLine();
  }

 }

 // 显示器
 public class Display {
  public static void ShowMsg(Object sender, Heater.BoiledEventArgs e) { //静态方法
   Heater heater = (Heater)sender;
   Console.WriteLine("Display：{0} - {1}: ", heater.area, heater.type);
   Console.WriteLine("Display：水快烧开了，当前温度：{0}度。", e.temperature);
   Console.WriteLine();
  }
 }

 class Program {
  static void Main() {
   Heater heater = new Heater();
   Alarm alarm = new Alarm();

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

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

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