假设我们有个高档的热水器(Heater)，我们给它通上电，当水温超过95度的时候：1、扬声器(Alarm)会开始发出语音，告诉你水的温度；2、液晶屏(Display)也会改变水温的显示，来提示水已经快烧开了。

可以建立如下事件与委托（在控制台下实现）：

Heater.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication2
{
    public class Heater
    {
        int temperature;
        public string bread = "007";
        public delegate void Handle(object obj,BoiledEventArgs e);
        public event Handle Boiled;

        public class BoiledEventArgs:EventArgs
        {
            public readonly int temperature;
            public BoiledEventArgs(int temperature)
            {
                this.temperature = temperature;
            }
        }

        protected virtual void OnBoiled(BoiledEventArgs e)
        {
            if (Boiled != null)
                Boiled(this, e);
        }

        public void BoilWater()
        {
            for (int i = 0; i <= 100; i++)
            {
                temperature = i;
                if (temperature > 95)
                {
                    if (Boiled != null)
                    {
                        BoiledEventArgs e = new BoiledEventArgs(temperature);
                        OnBoiled(e);
                    }
                }
            }
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication2
{
    public class Display
    {
        public static void ShowMsg(object obj,Heater.BoiledEventArgs e)
        {
            Heater heater = (Heater)obj;
            Console.WriteLine("{0}：警告：水已经{1}度了！！", heater.bread, e.temperature.ToString());
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication2
{
    public class Alarm
    {
        public void MakeAlert(object obj, Heater.BoiledEventArgs e)
        {
            Heater heater = (Heater)obj;
            Console.WriteLine("{0}：水已经{1}度了！", heater.bread, e.temperature.ToString());
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {
            Heater heater = new Heater();
            Alarm alarm=new Alarm();
            heater.Boiled += alarm.MakeAlert;
            heater.Boiled += Display.ShowMsg;
            heater.BoilWater();
            Console.ReadKey();
        }
    }
}