using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Timers;

namespace ConsoleAppTestDemo1
{
    public delegate void OrdereventHandler(Customer customer, OrderEventArgs e);

    public class OrderEventArgs : EventArgs
    {
        public string DishName { get; set; }
        public string Size { get; set; }

    }

    public class Customer
    {
        private OrdereventHandler ordereventHandler;

        public event OrdereventHandler Order
        {
            add
            {
                this.ordereventHandler += value;
            }

            remove
            {
                this.ordereventHandler -= value;
            }
        }

        public double Bill { get; set; }
        public void PayTheBill()
        {
            Console.WriteLine($"I will pay ${this.Bill}");
        }

        public void WalkIn()
        {
            Console.WriteLine("Wakl into the restaurant.");
        }

        public void SiteDown()
        {
            Console.WriteLine("Sit down");
        }

        public void Think()
        {
            for (int i = 0; i < 5; i++)
            {
                Console.WriteLine("Let me think");
                Thread.Sleep(1000);
            }

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

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

    public class Waiter
    {
        public void Action(Customer customer, OrderEventArgs e)
        {
            Console.WriteLine($"I will server you then dish - {e.DishName} {e.Size}");
            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;
        }
    }

    class TestDemo1
    {

        static void Main(string[] args)
        {
            Customer customer = new Customer();
            Waiter waiter = new Waiter();
            customer.Order += waiter.Action;

            customer.Action();
            customer.PayTheBill();

            Console.ReadLine();
        }
    }
}

Wakl into the restaurant.
Sit down
Let me think
Let me think
Let me think
Let me think
Let me think
I will server you then dish - Kongpao Chicken large
I will pay $15

请按任意键继续. . .