自定义事件的两种方式

完整版：

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

namespace EventLearning2
{
    class Program
    {
        static void Main(string[] args)
        {
            Customer customer = new Customer();//事件拥有者
            Waiter waiter = new Waiter();//事件响应者
            customer.Order += waiter.Action;//Order是事件，事件的订阅，action是事件处理器
            customer.Action();
            customer.PayTheBill();


        }
    }

    public class OrderEventArgs:EventArgs//定义消息
    {
        public string DishName { get; set; }
        public string Size { get; set; }
    }

    public delegate void OrderEventHandler(Customer customer, OrderEventArgs e);//声明委托类型


    public class Customer
    {
        public double Bill { get; set; }
        private OrderEventHandler orderEventHandler;//委托字段
        public event OrderEventHandler Order//声明事件
        {
            add
            {
                this.orderEventHandler += value;//事件添加器，加等于外界传进来的事件处理器
            }
            remove
            {
                this.orderEventHandler -= value;
            }
        }
        public void PayTheBill()
        {
            Console.WriteLine("I will pay {0}",this.Bill);
        }

        public void WalkIn()
        {
            Console.WriteLine("I walk in the restaurant");
        }

        public void SitDown()
        {
            Console.WriteLine("I sit down");
        }

        public void Think()
        {
            for (int i = 0; i < 5; i++)
            {
                Console.WriteLine("Let me think...");
                Thread.Sleep(500);
            }

            if (this.orderEventHandler!=null)
            {
                OrderEventArgs e = new OrderEventArgs();
                e.DishName = "ShuanYangRou";
                e.Size = "large";
                this.orderEventHandler.Invoke(this, e);
            }
        }

        public void Action()
        {
            Console.ReadLine();
            this.WalkIn();
            this.SitDown();
            this.Think();
        }


    }

    public class Waiter
    {
        internal void Action(Customer customer, OrderEventArgs e)
        {
            Console.WriteLine("I will serve you the dish-{0}",e.DishName);
            double price = 10;
            switch (e.Size)
            {
                case "small":
                    price = price * 0.5;
                    break;
                case "large":
                    price = price * 1.5;
                    break;
                default:
                    break;
            }

            customer.Bill += price;
        }
    }

}

简化声明: