C#多线程技术总结（同步）

二、串行（同步）：

1.lock、Monitor--注意锁定的对象必需是引用类型（string类型除外）

示例：

        private static object syncObject = new object();

        private static void TaskWork(object i)
        {
            Console.WriteLine("我是任务：{0}",i);
            lock (syncObject)
            {
                Thread.Sleep(1000);
                Console.WriteLine("我是任务：{0},线程ID:{1}",i,Thread.CurrentThread.ManagedThreadId);
            }

            try
            {
                Monitor.Enter(syncObject);
                Console.WriteLine("我是任务：{0},线程ID:{1}", i, Thread.CurrentThread.ManagedThreadId);
            }
            finally
            {
                Monitor.Exit(syncObject);
            }
        }

//调用
Task.Factory.StartNew(TaskWork,1);
Task.Factory.StartNew(TaskWork, 2);

2.Interlocked

示例：

            int i=1;
            Interlocked.Increment(ref i); //增量+1=2;
            Console.WriteLine("i当前的值：{0}", i);

            Interlocked.Decrement(ref i); //减量-1=0;
            Console.WriteLine("i当前的值：{0}", i);

            Interlocked.Exchange(ref i, 2);//赋值=2;
            Console.WriteLine("i当前的值：{0}",i);

            Interlocked.CompareExchange(ref i, 10, 2);//比较交换值，当i=2时，则将i赋值为10；
            Console.WriteLine("i当前的值：{0}", i);

3.Mutex--可以实现进程间的同步，甚至是两个远程进程间的同步

示例：

            var t1 = new Task(() =>
            {
                Console.WriteLine("我是第一个任务！");
                Mutex m = new Mutex(false, "test");
                m.WaitOne();
                Console.WriteLine("第一个任务完成！");
                m.ReleaseMutex();
            });

            var t2 = new Task(() =>
            {
                Console.WriteLine("我是第二个任务！");
                Mutex m = new Mutex(false, "test");
                m.WaitOne();
                Console.WriteLine("第二个任务完成！");
                m.ReleaseMutex();
            });

            t1.Start();
            t2.Start();

 4.ReaderWriterLock 、ReaderWriterLockSlim--如果在某一时刻资源并没有获取写的独占权,那么可以获得多个读的访问权,单个写入的独占权,如果某一时刻已经获取了写入的独占权,那么其它读取的访问权必须进行等待. 

示例：

        static ReaderWriterLock rwLock = new ReaderWriterLock();

        static void Read(object state)
        {
            Console.WriteLine("我是读线程，线程ID是：{0}",Thread.CurrentThread.ManagedThreadId);
            rwLock.AcquireReaderLock(Timeout.Infinite);//无限期等待,需要显式调用ReleaseReaderLock释放锁
            var readList = state as IEnumerable<int>;
            foreach (int item in readList)
            {
                Console.WriteLine("读取当前的值为：{0}", item);
                Thread.Sleep(500);
            }
            Console.WriteLine("读完成，线程ID是：{0}", Thread.CurrentThread.ManagedThreadId);
            rwLock.ReleaseReaderLock();
            
        }


        static void Write(object state)
        {
            Console.WriteLine("我是写线程，线程ID是：{0}", Thread.CurrentThread.ManagedThreadId);
            rwLock.AcquireWriterLock(Timeout.Infinite); //无限期等待,需要显式调用ReleaseWriterLock释放锁
            var writeList = state as List<int>;
            int lastCount=writeList.Count();
            for (int i = lastCount; i <= 10+lastCount; i++)
            {
                writeList.Add(i);
                Console.WriteLine("写入当前值：{0}",i);
                Thread.Sleep(500);
            }
            Console.WriteLine("写完成，线程ID是：{0}", Thread.CurrentThread.ManagedThreadId);
            rwLock.ReleaseWriterLock();
        }

    //调用：
            var rwList = new List<int>();

            var t1 = new Thread(Write);
            var t2 = new Thread(Read);
            var t3 = new Thread(Write);
            var t4 = new Thread(Read);
            
            t1.Start(rwList);
            t2.Start(rwList);
            t3.Start(rwList);
            t4.Start(rwList);

5.SynchronizationAttribute--确保某个类的实例在同一时刻只能被一个线程访问，类的定义要求：A.类上必需标记SynchronizationAttribute特性，B.类必需继承自System.ContextBoundObject对象

示例：

    [Synchronization(SynchronizationAttribute.REQUIRED,true)]
    public class Account : System.ContextBoundObject
    {
        private static int _balance;
        public int Blance
        {
            get
            {
                return _balance;
            }
        }

        public Account()
        {
            _balance = 1000;
        }

        public void WithDraw(string name,object money)
        {
            if ((int)money <= _balance)
            {
                Thread.Sleep(2000);
                _balance = _balance - (int)money;
                Console.WriteLine("{0} 取钱成功！余额={1}", name, _balance);
            }
            else
            {
                Console.WriteLine("{0} 取钱失败！余额不足！", name);
            }
        }
    }

//调用：
            var account = new Account();
            Parallel.Invoke(() =>
            {
                account.WithDraw("张三",600);

            }, () =>
            {
                account.WithDraw("李四",600);
            });

6.MethodImplAttribute--使整个方法上锁，直到方法返回，才释放锁

示例：

    public class Account
    {
        private static int _balance;
        public int Blance
        {
            get
            {
                return _balance;
            }
        }

        public Account()
        {
            _balance = 1000;
        }

        [MethodImpl(MethodImplOptions.Synchronized)]
        public void WithDraw(string name,object money)
        {
            if ((int)money <= _balance)
            {
                Thread.Sleep(2000);
                _balance = _balance - (int)money;
                Console.WriteLine("{0} 取钱成功！余额={1}", name, _balance);
            }
            else
            {
                Console.WriteLine("{0} 取钱失败！余额不足！", name);
            }
        }
    }

//调用
            var account = new Account();
            Parallel.Invoke(() =>
            {
                account.WithDraw("张三",600);

            }, () =>
            {
                account.WithDraw("李四",600);
            });

7.AutoResetEvent、ManualResetEvent、ManualResetEventSlim--调用WaitOne、WaitAny或WaitAll来使线程等待事件,调用Set方法发送信号，事件将变为终止状态，等待的线程被唤醒

示例：

            AutoResetEvent arEvent = new AutoResetEvent(false);//默认为无信号，处于非终止状态
            Task.Factory.StartNew((o) => {
                for (int i = 1; i <= 10; i++)
                {
                    Console.WriteLine("循环第{0}次",i);
                }
                arEvent.Set();//发送信号，处于终止状态
            },arEvent);


            arEvent.WaitOne();//等待信号，收到信号后则继续下面的执行

            Console.WriteLine("我是主线程，我继续执行！");
            Console.Read();

 8.Sempaphore、SemaphoreSlim（不可跨进程）--信号量，可实现线程、进程间同步

示例：

    public class WashRoom
    {
        private readonly Semaphore sem;

        public WashRoom(int maxUseableCount)
        {
            sem = new Semaphore(maxUseableCount, maxUseableCount, "WC");
        }

        public void Use(int i)
        {
            Task.Factory.StartNew(() =>
                {
                    Console.WriteLine("第{0}个人等待进入", i);
                    // WaitOne:如果还有“空位”，则占位，如果没有空位，则等待；
                    sem.WaitOne();
                    Console.WriteLine("第{0}个人成功进入，使用中", i);
                    // 模拟线程执行了一些操作
                    Thread.Sleep(100);
                    Console.WriteLine("第{0}个人用完，离开了", i);
                    // Release:释放一个“空位”
                    sem.Release();
                });
        }
    }

//调用：
            var wc = new WashRoom(5);
            for (int i = 1; i <= 7; i++)
            {
                wc.Use(i);
            }

9.Barrier--屏障，使多个任务能够采用并行方式依据某种算法在多个阶段中协同工作，即：将一个阶段的事情分成多个线程来异步执行，执行完毕后再同时进入下一个阶段

示例：

            int taskSize = 5;
            Barrier barrier = new Barrier(taskSize, (b) =>
            {
                Console.WriteLine(string.Format("{0}当前阶段编号：{1}{0}", "-".PadRight(15, '-'), b.CurrentPhaseNumber));
            });

            var tasks = new Task[taskSize];

            for (int i = 0; i < taskSize; i++)
            {
                tasks[i] = Task.Factory.StartNew((n) =>
                {
                    Console.WriteLine("Task : #{0}   ---->  处理了第一部份数据。", n);
                    barrier.SignalAndWait();

                    Console.WriteLine("Task : #{0}   ---->  处理了第二部份数据。", n);
                    barrier.SignalAndWait();

                    Console.WriteLine("Task : #{0}   ---->  处理了第三部份数据。", n);
                    barrier.SignalAndWait();

                }, i);
            }

            Task.WaitAll(tasks);

10.SpinLock--自旋锁,仅限锁定的时间较短

示例：

            SpinLock sLock = new SpinLock();
            int num = 0;
            Action action = () =>
            {
                bool lockTaken = false;
                for (int i = 0; i < 10; i++)
                {
                    lockTaken = false;
                    try
                    {
                        sLock.Enter(ref lockTaken);
                        Console.WriteLine("{0}+1={1} ---线程ID:[{2}]", num, ++num,Thread.CurrentThread.ManagedThreadId);
                        Thread.Sleep(new Random().Next(9));
                    }
                    finally
                    {
                        //真正获取之后，才释放
                        if (lockTaken) sLock.Exit();
                    }
                }
            };

//多线程调用：
            Parallel.Invoke(action, action, action);
            Console.WriteLine("合计：{0}", num);

11.SpinWait--自旋等待，轻量级

            Thread.Sleep(1000);//线程等待1S;
            Console.WriteLine(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff"));

            SpinWait.SpinUntil(() => false, 1000);//自旋等待1S
            Console.WriteLine(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff"));

            Thread.SpinWait(100000);//指定CPU的循环次数，时间间隔处决于处理器的运行速度,一般不建议使用
            Console.WriteLine(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff"));

12.CountdownEvent--与Sempaphore功能类似，但CountdownEvent支持动态调整信号计数

 示例：

        static void TimeLimitShopping(int custCount,int times,CountdownEvent countdown)
        {
            var customers = Enumerable.Range(1, custCount);
            foreach (var customer in customers)
            {
                int currentCustomer = customer;
               Task.Factory.StartNew(()=>
                {
                    SpinWait.SpinUntil(() => false, 1000);
                    Console.WriteLine("第{0}波客户购买情况：Customer-{1}-已购买.", times, currentCustomer);
                    countdown.Signal();
                });
                //countdown.AddCount();
            }
        }


//调用：
var countdown = new CountdownEvent(5);
                TimeLimitShopping(5, 1, countdown);
                countdown.Wait();


                countdown.Reset(10);
                TimeLimitShopping(10, 2, countdown);
                countdown.Wait();

                countdown.Reset(20);
                TimeLimitShopping(20, 3, countdown);
                countdown.Wait();

 最后分享在System.Collections.Concurrent命名空间下的几个并发集合类：

ConcurrentBag<T>：表示线程安全的无序集合；

ConcurrentDictionary<T>：表示线程安全的多个键值对集合；

ConcurrentQueue<T>：表示线程安全的先进先出集合；

ConcurrentStack<T>：表示线程安全的后进先出集合；

线程的几个状态(以下图片来源于这篇文章：http://www.cnblogs.com/edisonchou/p/4848131.html)：

参考以下相关文章：

归纳一下:C#线程同步的几种方法

C#编程总结（三）线程同步