C#常用多线程方法

1.  Thread类

C#多线程编程中Thread类需要包含名称空间System.Threading。

class Program
    {
        static void Main(string[] args)
        {
            Thread thread01 = new Thread(ThreadTask01);
            thread01.Start();
           // thread01.Join();

            for (int i = 0; i < 5; i++)
            {
                Console.WriteLine("Thread Main is working !");
                Thread.Sleep(20);
            }

            Console.ReadKey();

        }
        static void ThreadTask01()
        {
            for (int i = 0; i < 5; i++)
            {
                Console.WriteLine("Thread task one is working !");
                Thread.Sleep(20);
            }
        }
    }

输出：

Start不会阻塞主线程，如果加入Join，则会阻塞主线程的执行，直到子线程执行完成才把控制权交还给主流程，但是各个子线程之间的并行执行不受Join影响。上例中加入Join的输出：

多个线程同时访问一个公共字段时，容易引起线程安全问题，C#中使用关键字lock保证数据的安全性和同步：

class Program
    {
        //static readonly object locker = new object();
        static int TotalNum = 100;

        static void Main(string[] args)
        {
            Thread thread01 = new Thread(ThreadTask01);
            Thread thread02 = new Thread(ThreadTask02);
            thread01.Start();
            thread02.Start();

            Console.ReadKey();

        }
        static void ThreadTask01()
        {
            while (TotalNum > 0)
            {
                Console.WriteLine(TotalNum);
                TotalNum--;
                Thread.Sleep(10);
            }
        }

        static void ThreadTask02()
        {
            while (TotalNum > 0)
            {
                Console.WriteLine(TotalNum);
                TotalNum--;
                Thread.Sleep(10);
            }
        }
    }

输出异常，中间有重复输出的数字：

添加lock：

class Program
    {
        static readonly object locker = new object();
        static int TotalNum = 100;

        static void Main(string[] args)
        {
            Thread thread01 = new Thread(ThreadTask01);
            Thread thread02 = new Thread(ThreadTask02);
            thread01.Start();
            thread02.Start();

            Console.ReadKey();

        }
        static void ThreadTask01()
        {
            while (TotalNum > 0)
            {
                lock (locker)
                {
                    Console.WriteLine(TotalNum);
                    TotalNum--;
                }
                Thread.Sleep(10);
            }
        }

        static void ThreadTask02()
        {
            while (TotalNum > 0)
            {
                lock (locker)
                {
                    Console.WriteLine(TotalNum);
                    TotalNum--;
                }
                Thread.Sleep(10);
            }
        }
    }

输出正常：

2. ParameterThreadStart委托

ParameterThreadStart委托定义为 void ParameterizedThreadStart(Object state)。

class Program
    {
        static int totalNum = 10;
        static void Main(string[] args)
        {
            ParameterizedThreadStart thread01 = new ParameterizedThreadStart(ThreadTask01);
            Thread thread = new Thread(thread01);
            thread.Start(totalNum);
            Console.ReadKey();

        }
        static void ThreadTask01(object obj)
        {
            for (int i = 0; i < Convert.ToInt32(obj); i++)
            {
                Console.WriteLine(i);
                Thread.Sleep(10);
            }
        }
    }

3. 匿名方法

匿名方法启动多线程是使用Thread类的另一种更加灵活的方法。

class Program
    {
        static void Main(string[] args)
        {
            ThreadStart threadStart = new ThreadStart(delegate ()
              {
                  for (int i = 0; i < 5; i++)
                  {
                      Console.WriteLine("Thread one is working!");
                  }
              });
            Thread thread = new Thread(threadStart);
            thread.Start();//多线程启动匿名方法
            //等待线程结束
            while (thread.ThreadState != ThreadState.Stopped)
            {
                Thread.Sleep(10);
            }
            Console.ReadKey();
        }

    }

4. Delegate委托

委托是一种比较高级的多线程方法，可以传入参数和获取返回值，还可以查询异步操作是否完成。

class Program
    {
        private delegate int NewTaskDelegate(int ms);
        private static int newTask(int ms)
        {
            Console.WriteLine("任务开始");
            Thread.Sleep(ms);
            Random random = new Random();
            int n = random.Next(10000);
            Console.WriteLine("任务完成");
            return n;
        }
        static void Main(string[] args)
        {
            NewTaskDelegate task = newTask;
            IAsyncResult asyncResult = task.BeginInvoke(2000, null, null);
            //EndInvoke方法将被阻塞2秒

            //使用WaitOne阻塞主线程，直到子线程完成操作
            while (!asyncResult.AsyncWaitHandle.WaitOne(100, false))
            {
                Console.Write("-");
            }

            while (!asyncResult.IsCompleted)  //查询线程是否完成
            {
                Console.Write("*");
                Thread.Sleep(100);
            }
            int result = task.EndInvoke(asyncResult);
            Console.WriteLine(result);
            Console.Read();
        }
    }