using System;

namespace EventAndDelegateTest
{
    class Program
    {
        static void Main(string[] args)
        {
            Dog dog = new Dog();
            Host host = new Host(dog);

            //当前时间，从2008年12月31日23:59:50开始计时
            DateTime now = new DateTime(2020, 12, 31, 23, 59, 50);
            DateTime midnight = new DateTime(2021, 1, 1, 0, 0, 0);

            //等待午夜的到来
            Console.WriteLine("时间一秒一秒地流逝... ");
            while (now < midnight)
            {
                Console.WriteLine("当前时间: " + now);
                System.Threading.Thread.Sleep(1000);    //程序暂停一秒
                now = now.AddSeconds(1);                //时间增加一秒
            }
            Console.WriteLine("小偷趁夜色潜入了房中.....");
            dog.OnAlarm();

            Console.ReadLine();
        }
    }

    //事件发起者
    class Dog
    {
        //定义委托
        public delegate void DogAlarmEventHandler(object sender, EventArgs args);

        //声明事件
        public event DogAlarmEventHandler AlarmEvent;

        //引发事件的函数
        public void OnAlarm()
        {
            //如果事件不为空
            if(AlarmEvent != null)
            {
                Console.WriteLine("狗叫了");
                this.AlarmEvent(this, new EventArgs());
            }
        }
    }


    //事件接收者（使用者）
    class Host
    {
        //注册事件程序
        public Host(Dog dog)
        {
            dog.AlarmEvent += new Dog.DogAlarmEventHandler(HostHandlerAlarm);
        }

        //事件处理程序
        void HostHandlerAlarm(object sender, EventArgs e)
        {
            Console.WriteLine("主人抓住了小偷");
        }
    }
}