C#事件的自定义声明

资料来源于刘铁猛的视频

1 完整申明

using System;
using System.Threading;
using System.Windows.Forms;

namespace EventExample
{

    class Program
    {
        static void Main(string[] args)
        {
            Customer customer = new Customer();
            Waitor waitor = new Waitor();
            customer.Order += waitor.Action;
            customer.Action();
            customer.PayTheBill();
        }
    }
    public class OrderEventArgs : EventArgs
    {
        public string DishName { get; set; }
        public string Size { get; set; }
    }

    public delegate void OrderEventHandler(Customer customer/*事件拥有者*/, OrderEventArgs e);
    public class Customer
    {
        private OrderEventHandler orderEventHandler;
        //申明事件
        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 ${0}.", this.Bill);
        }

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

        public void SitDown()
        {
            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";
                e.Size = "large";
                this.orderEventHandler.Invoke(this, e);
            }
        }

        public void Action()
        {
            Console.ReadLine();//程序需要等一会儿
            this.WalkIn();
            this.SitDown();
            this.Think();
        }
    }

    class Waitor
    {
        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 *= 0.5;
                    break;
                case "large":
                    price *= 2;
                    break;
                default:
                    break;
            }
            //throw new NotImplementedException();
            customer.Bill += price;
        }
    }
}

2 简化申明

using System;
using System.Threading;
using System.Windows.Forms;

namespace EventExample
{

    class Program
    {
        static void Main(string[] args)
        {
            Customer customer = new Customer();
            Waitor waitor = new Waitor();
            customer.Order += waitor.Action;
            customer.Action();
            customer.PayTheBill();
        }
    }
    public class OrderEventArgs : EventArgs
    {
        public string DishName { get; set; }
        public string Size { get; set; }
    }

    public delegate void OrderEventHandler(Customer customer/*事件拥有者*/, OrderEventArgs e);
    public class Customer
    {
        //简化申明事件
        public event OrderEventHandler Order;
        //完整申明
        //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 ${0}.", this.Bill);
        }

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

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

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

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

        public void Action()
        {
            Console.ReadLine();//程序需要等一会儿
            this.WalkIn();
            this.SitDown();
            this.Think();
        }
    }

    class Waitor
    {
        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 *= 0.5;
                    break;
                case "large":
                    price *= 2;
                    break;
                default:
                    break;
            }
            //throw new NotImplementedException();
            customer.Bill += price;
        }
    }
}

3 申明为委托字段时也可以运行

using System;
using System.Threading;
using System.Windows.Forms;

namespace EventExample
{

    class Program
    {
        static void Main(string[] args)
        {
            Customer customer = new Customer();
            Waitor waitor = new Waitor();
            customer.Order += waitor.Action;


            customer.Action();
            customer.PayTheBill();
        }
    }
    public class OrderEventArgs : EventArgs
    {
        public string DishName { get; set; }
        public string Size { get; set; }
    }

    public delegate void OrderEventHandler(Customer customer/*事件拥有者*/, OrderEventArgs e);
    public class Customer
    {
        //申明一个委托字段
        public  OrderEventHandler Order; //
        //完整申明
        //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 ${0}.", this.Bill);
        }

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

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

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

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

        public void Action()
        {
            Console.ReadLine();//程序需要等一会儿
            this.WalkIn();
            this.SitDown();
            this.Think();
        }
    }

    class Waitor
    {
        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 *= 0.5;
                    break;
                case "large":
                    price *= 2;
                    break;
                default:
                    break;
            }
            //throw new NotImplementedException();
            customer.Bill += price;
        }
    }
}

4 但这样可能会出错，不是我们所希望的。

using System;
using System.Threading;
using System.Windows.Forms;

namespace EventExample
{

    class Program
    {
        static void Main(string[] args)
        {
            Customer customer = new Customer();
            Waitor waitor = new Waitor();
            customer.Order += waitor.Action;

            OrderEventArgs e = new OrderEventArgs();
            e.DishName = "TuDouSi";
            e.Size = "large";

            OrderEventArgs e2 = new OrderEventArgs();
            e2.DishName = "Beer";
            e2.Size = "large";

            //这样外面可以访问了
            Customer badGuy = new Customer();  //badguy给别人点菜了
            badGuy.Order += waitor.Action;
            badGuy.Order.Invoke(customer, e);
            badGuy.Order.Invoke(customer, e2);

            customer.PayTheBill();
        }
    }
    public class OrderEventArgs : EventArgs
    {
        public string DishName { get; set; }
        public string Size { get; set; }
    }

    public delegate void OrderEventHandler(Customer customer/*事件拥有者*/, OrderEventArgs e);
    public class Customer
    {
        //申明一个委托字段
        public  OrderEventHandler Order; //
        //完整申明
        //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 ${0}.", this.Bill);
        }

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

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

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

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

        public void Action()
        {
            Console.ReadLine();//程序需要等一会儿
            this.WalkIn();
            this.SitDown();
            this.Think();
        }
    }

    class Waitor
    {
        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 *= 0.5;
                    break;
                case "large":
                    price *= 2;
                    break;
                default:
                    break;
            }
            //throw new NotImplementedException();
            customer.Bill += price;
        }
    }
}

不要用3，4 

自带的EventHandler使用

using System;
using System.Threading;
using System.Windows.Forms;

namespace EventExample
{

    class Program
    {
        static void Main(string[] args)
        {
            Customer customer = new Customer();
            Waitor waitor = new Waitor();
            customer.Order += waitor.Action;
            customer.Action();
            customer.PayTheBill();
        }
    }
    public class OrderEventArgs : EventArgs
    {
        public string DishName { get; set; }
        public string Size { get; set; }
    }

    //public delegate void OrderEventHandler(Customer customer/*事件拥有者*/, OrderEventArgs e);
    public class Customer
    {
        
        public event EventHandler Order; //关键是event

        public double Bill { get; set; }
        public void PayTheBill()
        {
            Console.WriteLine("I will pay ${0}.", this.Bill);
        }

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

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

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

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

        public void Action()
        {
            Console.ReadLine();//程序需要等一会儿
            this.WalkIn();
            this.SitDown();
            this.Think();
        }
    }

    class Waitor
    {
        internal void Action(object sender, EventArgs e)
        {
            Customer customer = sender as Customer;
            OrderEventArgs orderInfo = e as OrderEventArgs;
            Console.WriteLine("I will serve you the dish {0}", orderInfo.DishName);
            double price = 10;
            switch (orderInfo.Size)
            {
                case "small":
                    price *= 0.5;
                    break;
                case "large":
                    price *= 2;
                    break;
                default:
                    break;
            }
            //throw new NotImplementedException();
            customer.Bill += price;
        }
    }
}

using System;
using System.Threading;
using System.Windows.Forms;

namespace EventExample
{

    class Program
    {
        static void Main(string[] args)
        {
            Customer customer = new Customer();
            Waitor waitor = new Waitor();
            customer.Order += waitor.Action;
            customer.Action();
            customer.PayTheBill();
        }
    }
    public class OrderEventArgs : EventArgs
    {
        public string DishName { get; set; }
        public string Size { get; set; }
    }

    //public delegate void OrderEventHandler(Customer customer/*事件拥有者*/, OrderEventArgs e);
    public class Customer
    {
        
        public  event EventHandler Order; //
        //完整申明
        //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 ${0}.", this.Bill);
        }

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

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

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

            this.OnOrder("Tudousi", "large");
        }

        protected void OnOrder(string dishName, string size)
        {
            OrderEventArgs e = new OrderEventArgs();
            e.DishName = dishName;
            e.Size = size;
            this.Order.Invoke(this, e);
        }
        

        public void Action()
        {
          //  Console.ReadLine();//程序需要等一会儿
            this.WalkIn();
            this.SitDown();
            this.Think();
        }
    }

    class Waitor
    {
        internal void Action(object sender, EventArgs e)
        {
            Customer customer = sender as Customer;
            OrderEventArgs orderInfo = e as OrderEventArgs;
            Console.WriteLine("I will serve you the dish {0}", orderInfo.DishName);
            double price = 10;
            switch (orderInfo.Size)
            {
                case "small":
                    price *= 0.5;
                    break;
                case "large":
                    price *= 2;
                    break;
                default:
                    break;
            }
            //throw new NotImplementedException();
            customer.Bill += price;
        }
    }
}

一个类对外的接口主要有三个：方法，属性，事件=== 做事件， 荐储数据，通知别人