简单的事件示例代码

简单的事件示例代码

简单的事件示例代码：

完整形式

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;

/*
 * 事件模型的五个组成部分
 * 1. 事件的拥有者(event source, 对象) 
 * 2. 事件的成员(event, 成员)
 * 3. 事件的响应者(event subscriber, 对象)
 * 4. 事件的处理器(event handler, 成员)
 * 5. 事件订阅 --- 把事件处理器与事件关联在一起，本质上是一种以委托类型为基础的“约定”
 */

namespace ConsoleAppTestDemo1
{
    // 委托类型声明
    public delegate void OrderEventHandler(Customer customer, OrderEventArgs e);

    // 事件的参数
    public class OrderEventArgs : EventArgs
    {
        public string DishName { get; set; }
        public string Size { get; set; }

    }

    // 事件的拥有者(event source) --- 客人
    public class Customer
    {
        // 委托类型的字段
        private OrderEventHandler ordereventHandler;

        // 事件成员(event) --- 委托字段的包装器，对委托字段的访问起限制作用
        public event OrderEventHandler Order
        {
            add
            {
                this.ordereventHandler += value;
            }

            remove
            {
                this.ordereventHandler -= value;
            }
        }

        // 需要支付的金额
        public double Bill { get; set; }

        // 付款
        public void PayTheBill()
        {
            Console.WriteLine($"I will pay ${this.Bill}");
        }

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

            this.OnOrder("Kongpao Chicken", "large");
        }

        // 触发事件，当存在事件的处理器时，处理该事件 --- 访问级别为 protected 不能为 public
        protected void OnOrder(string dishName, string size)
        {
            if (this.ordereventHandler != null)
            {
                OrderEventArgs e = new OrderEventArgs() { DishName = dishName, Size = size };
                this.ordereventHandler.Invoke(this, e);
            }

        }

        // 开始点菜，触发事件
        public void Action()
        {
            Console.WriteLine("start order dishes ...");
            this.ThinkDishes();
        }
    }

    // 事件的响应者(event subscriber) --- 服务员
    public class Waiter
    {
        // 事件处理器(event handler) --- 上菜计费
        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();
            // 事件订阅
            customer.Order += new OrderEventHandler(waiter.Action);

            // 点菜 -- 有服务员来处理
            customer.Action();
            // 付款
            customer.PayTheBill();

            // 点菜 -- 有服务员来处理
            customer.Action();
            // 付款
            customer.PayTheBill();

            // 取消订阅
            customer.Order -= new OrderEventHandler(waiter.Action);

            // 点菜 --- 没有服务员来处理
            customer.Action();
            // 付款
            customer.PayTheBill();

            Console.ReadLine();
        }
    }
}

简单形式

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;

/*
 * 事件模型的五个组成部分
 * 1. 事件的拥有者(event source, 对象) 
 * 2. 事件的成员(event, 成员)
 * 3. 事件的响应者(event subscriber, 对象)
 * 4. 事件的处理器(event handler, 成员)
 * 5. 事件订阅 --- 把事件处理器与事件关联在一起，本质上是一种以委托类型为基础的“约定”
 */

namespace ConsoleAppTestDemo1
{

    // 事件的参数
    public class OrderEventArgs : EventArgs
    {
        public string DishName { get; set; }
        public string Size { get; set; }

    }

    // 事件的拥有者(event source) --- 客人
    public class Customer
    {

        // 事件成员(event) --- 委托字段的包装器，对委托字段的访问起限制作用
        public event EventHandler<OrderEventArgs> Order;

        // 需要支付的金额
        public double Bill { get; set; }

        // 付款
        public void PayTheBill()
        {
            Console.WriteLine($"I will pay ${this.Bill}");
        }

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

            this.OnOrder("Kongpao Chicken", "large");
        }

        // 触发事件，当存在事件的处理器时，处理该事件
        protected void OnOrder(string dishName, string size)
        {
            if (this.Order != null)
            {
                OrderEventArgs e = new OrderEventArgs() { DishName = dishName, Size = size };
                this.Order.Invoke(this, e);
            }

        }

        // 开始点菜，触发事件
        public void Action()
        {
            Console.WriteLine("start order dishes ...");
            this.ThinkDishes();
        }
    }

    // 事件的响应者(event subscriber) --- 服务员
    public class Waiter
    {
        // 事件处理器(event handler) --- 上菜计费
        public void Action(object sender, OrderEventArgs e)
        {
            Customer customer = sender as Customer;

            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();
            // 事件订阅
            customer.Order += waiter.Action;
            // 点菜 -- 有服务员来处理
            customer.Action();
            // 付款
            customer.PayTheBill();

            // 点菜 -- 有服务员来处理
            customer.Action();
            // 付款
            customer.PayTheBill();

            // 取消订阅
            customer.Order -= waiter.Action;

            // 点菜 --- 没有服务员来处理
            customer.Action();
            // 付款
            customer.PayTheBill();

            Console.ReadLine();
        }
    }
}

输出信息：

start order dishes ...
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
start order dishes ...
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 $30
start order dishes ...
Let me think
Let me think
Let me think
Let me think
Let me think
I will pay $30

请按任意键继续. . .

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