本文主要讲述了多线程开发中经典示例，通过本示例，可以加深对多线程的理解。

示例概述：

下面用一个模拟吃苹果的实例，说明C#中多线程的实现方法。要求开发一个程序实现如下情况：一个家庭有三个孩子，爸爸妈妈不断削苹果往盘子里面放，老大、老二、老三不断从盘子里面取苹果吃。盘子的大小有限，最多只能放5个苹果，并且爸妈不能同时往盘子里面放苹果，妈妈具有优先权。三个孩子取苹果时，盘子不能为空，三人不能同时取，老三优先权最高，老大最低。老大吃的最快，取的频率最高，老二次之。

涉及到知识点：

• 线程Thread 创建并控制线程，设置其优先级并获取其状态。
• 锁 lock 用于实现多线程同步的最直接办法就是加锁，它可以把一段代码定义为互斥段，在一个时刻内只允许一个线程进入执行，而其他线程必须等待。
• 事件EventHandler 声明一个事件，用于通知界面做改变

设计思路：

• Productor 表示生产者，用于削苹果。
• Consumer 表示消费者，用于吃苹果。
• Dish 盘子，用于装苹果，做为中间类
• EatAppleSmp 的BeginEat()方法，表示开始吃苹果，启动线程

效果图如下【爸爸妈妈削苹果，孩子吃苹果】：

后台输出如下：

Mama放1个苹果Baba放1个苹果Dage取苹果吃...Erdi取苹果吃...Sandi等待取苹果Mama放1个苹果Sandi取苹果吃...Baba放1个苹果Dage取苹果吃...Mama放1个苹果Baba放1个苹果Erdi取苹果吃...Mama放1个苹果Baba放1个苹果Dage取苹果吃...Sandi取苹果吃...Mama放1个苹果Baba放1个苹果Erdi取苹果吃...Mama放1个苹果Baba放1个苹果Dage取苹果吃...Mama放1个苹果Baba放1个苹果Sandi取苹果吃...Mama放1个苹果Baba正在等待放入苹果Erdi取苹果吃...Baba放1个苹果Dage取苹果吃...Mama放1个苹果Baba正在等待放入苹果Mama正在等待放入苹果Sandi取苹果吃...Baba放1个苹果Mama正在等待放入苹果Erdi取苹果吃...Mama放1个苹果Dage取苹果吃...Baba放1个苹果Mama正在等待放入苹果Dage取苹果吃...Mama放1个苹果Baba正在等待放入苹果Erdi取苹果吃...Baba放1个苹果Sandi取苹果吃...Mama放1个苹果Baba正在等待放入苹果Dage取苹果吃...Baba放1个苹果Mama正在等待放入苹果Erdi取苹果吃...Mama放1个苹果Baba正在等待放入苹果Sandi取苹果吃...Baba放1个苹果Mama正在等待放入苹果Dage取苹果吃...Mama放1个苹果Baba正在等待放入苹果Mama正在等待放入苹果Erdi取苹果吃...Mama放1个苹果Baba正在等待放入苹果Dage取苹果吃...Baba放1个苹果Mama正在等待放入苹果Sandi取苹果吃...Mama放1个苹果Baba正在等待放入苹果Mama正在等待放入苹果线程 'Mama' (0x1ce0) 已退出，返回值为 0 (0x0)。线程 'Baba' (0x1888) 已退出，返回值为 0 (0x0)。Erdi取苹果吃...Dage取苹果吃...Sandi取苹果吃...Dage取苹果吃...Erdi取苹果吃...Dage等待取苹果Sandi等待取苹果Erdi等待取苹果后台输出

Productor 代码如下：

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading;namespace DemoSharp.EatApple{ /// <summary> /// 生产者 /// </summary> public class Productor { private Dish dish; private string name; public string Name { get { return name; } set { name = value; } } public EventHandler PutAction;//声明一个事件，当放苹果时触发该事件 public Productor(string name, Dish dish) { this.name = name; this.dish = dish; } public void run() { while (true) { bool flag= dish.Put(name); if (flag) { if (PutAction != null) { PutAction(this, null); } try { Thread.Sleep(600);//削苹果时间 } catch (Exception ex) { } } else { break; } } } }}

Consumer代码如下：

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading;namespace DemoSharp.EatApple{ /// <summary> /// 消费者 /// </summary> public class Consumer { private string name; public string Name { get { return name; } set { name = value; } } private Dish dish; private int timelong; public EventHandler GetAction;//声明一个事件，当放苹果时触发该事件 public Consumer(string name, Dish dish, int timelong) { this.name = name; this.dish = dish; this.timelong = timelong; } public void run() { while (true) { bool flag= dish.Get(name); if (flag) { //如果取到苹果，则调用事件，并开始吃 if (GetAction != null) { GetAction(this, null); } try { Thread.Sleep(timelong);//吃苹果时间 } catch (ThreadInterruptedException) { } } else { break; } } } }}

Dish代码如下：

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading;namespace DemoSharp.EatApple{ /// <summary> /// 盘子，属于中间类 /// </summary> public class Dish { private int f = 5;//表示盘子中还可以放几个苹果，最多只能放5个苹果 private int EnabledNum;//可放苹果总数 private int n = 0; //表示已经放了多少个苹果 private object objGet = new object(); private object objPut = new object(); /// <summary> /// 构造函数，初始化Dish对象 /// </summary> /// <param name="num">表示削够多少个苹果结束</param> public Dish(int num) { this.EnabledNum = num; } /// <summary> /// 放苹果的方法 /// </summary> /// <param name="name"></param> ///<returns>是否放成功</returns> public bool Put(string name) { lock (this)//同步控制放苹果 { bool flag = false; while (f == 0)//苹果已满，线程等待 { try { System.Console.WriteLine(name + "正在等待放入苹果"); Monitor.Wait(this); } catch (Exception ex) { System.Console.WriteLine(name + "等不及了"); } } if (n < EnabledNum) { f = f - 1;//削完一个苹果放一次 n = n + 1; System.Console.WriteLine(name + "放1个苹果"); flag = true; } Monitor.PulseAll(this); return flag; } } /// <summary> /// 取苹果的方法 /// </summary> /// <param name="name"></param> public bool Get(string name) { lock (this)//同步控制取苹果 { bool flag = false; while (f == 5) { try { System.Console.WriteLine(name + "等待取苹果"); Monitor.Wait(this); } catch (ThreadInterruptedException) { } } if (n <= EnabledNum) { f = f + 1; System.Console.WriteLine(name + "取苹果吃..."); flag = true; } Monitor.PulseAll(this); return flag; } } } }

EatAppleSmp代码如下：

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading;namespace DemoSharp.EatApple{ public class EatAppleSmp { public EventHandler PutAction;//声明一个事件，当放苹果时触发该事件 public EventHandler GetAction;//声明一个事件，当放苹果时触发该事件 /// <summary> /// 开始吃苹果 /// </summary> public void BeginEat() { Thread th_mother, th_father, th_young, th_middle, th_old;//依次表示妈妈，爸爸，小弟，二弟，大哥 Dish dish = new Dish(30); Productor mother = new Productor("Mama", dish);//建立线程 mother.PutAction += PutActionMethod; Productor father = new Productor("Baba", dish); father.PutAction += PutActionMethod; Consumer old = new Consumer("Dage", dish, 1200); old.GetAction += GetActionMethod; Consumer middle = new Consumer("Erdi", dish, 1500); middle.GetAction += GetActionMethod; Consumer young = new Consumer("Sandi", dish, 1800); young.GetAction += GetActionMethod; th_mother = new Thread(new ThreadStart(mother.run)); th_mother.Name = "Mama"; th_father = new Thread(new ThreadStart(father.run)); th_father.Name = "Baba"; th_old = new Thread(new ThreadStart(old.run)); th_old.Name = "Dage"; th_middle = new Thread(new ThreadStart(middle.run)); th_middle.Name = "Erdi"; th_young = new Thread(new ThreadStart(young.run)); th_young.Name = "Sandi"; th_mother.Priority = ThreadPriority.Highest;//设置优先级 th_father.Priority = ThreadPriority.Normal; th_old.Priority = ThreadPriority.Lowest; th_middle.Priority = ThreadPriority.Normal; th_young.Priority = ThreadPriority.Highest; th_mother.Start(); th_father.Start(); th_old.Start(); th_middle.Start(); th_young.Start(); } private void GetActionMethod(object sender,EventArgs e) { if (GetAction != null) { GetAction(sender, e); } } private void PutActionMethod(object sender, EventArgs e) { if (PutAction != null) { PutAction(sender, e); } } }}

界面类代码如下：

using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Linq;using System.Text;using System.Windows.Forms;using DemoSharp.EatApple;namespace DemoSharp{ /// <summary> /// 页面类 /// </summary> public partial class EatAppleForm : Form { private EatAppleSmp m_EatAppleSmp = new EatAppleSmp(); public EatAppleForm() { InitializeComponent(); InitView(); m_EatAppleSmp.PutAction += PutActionMethod; m_EatAppleSmp.GetAction += GetActionMethod; } /// <summary> /// 初始化GroupBox /// </summary> private void InitView() { this.gbBaba.Controls.Clear(); this.gbMama.Controls.Clear(); this.gbDage.Controls.Clear(); this.gbErdi.Controls.Clear(); this.gbSandi.Controls.Clear(); } /// <summary> /// 启动线程 /// </summary> /// <param name="sender"></param> /// <param name="e"></param> private void btnStart_Click(object sender, EventArgs e) { this.m_EatAppleSmp.BeginEat(); } /// <summary> /// 放苹果事件 /// </summary> /// <param name="sender"></param> /// <param name="e"></param> private void PutActionMethod(object sender, EventArgs e) { Productor p = sender as Productor; if (p != null) { if (p.Name == "Baba") { AddItemToGroupBox(this.gbBaba, this.lblBaba); } if (p.Name == "Mama") { AddItemToGroupBox(this.gbMama, this.lblMama); } } } /// <summary> /// 吃苹果事件 /// </summary> /// <param name="sender"></param> /// <param name="e"></param> public void GetActionMethod(object sender, EventArgs e) { Consumer c = sender as Consumer; if (c != null) { if (c.Name == "Dage") { AddItemToGroupBox(this.gbDage, this.lblDage); } if (c.Name == "Erdi") { AddItemToGroupBox(this.gbErdi, this.lblErdi); } if (c.Name == "Sandi") { AddItemToGroupBox(this.gbSandi, this.lblSandi); } } } /// <summary> /// 往指定的GroupBox中添加对象 /// </summary> /// <param name="gbView"></param> /// <param name="lbl"></param> private void AddItemToGroupBox(GroupBox gbView,Label lbl) { gbView.Invoke(new Action(() => { PictureBox p = new PictureBox(); p.Width = 20; p.Height = 20; p.Dock = DockStyle.Left; p.Image = this.imgLst01.Images[0]; p.Margin = new Padding(2); gbView.Controls.Add(p); })); //显示个数 lbl.Invoke(new Action(() => { if (string.IsNullOrEmpty(lbl.Text)) { lbl.Text = "0"; } lbl.Text = (int.Parse(lbl.Text) + 1).ToString(); })); } }}

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