示例 3：使用线程池以下示例显示如何使用线程池。首先创建 ManualResetEvent 对象，此对象使程序能够知道线程池何时运行完所有的工作项。接着，尝试向线程池添加一个线程。如果添加成功，则添加其余的线程（本例中为 4 个）。然后线程池将工作项放入可用线程中。调用 eventX 上的 WaitOne 方法，这会使程序的其余部分等待，直到用 eventX.Set 方法触发事件为止。最后，程序打印出线程上的负载（实际执行某一特定工作项的线程）。 // SimplePool.cs// Simple thread pool exampleusing System;using System.Collections;using System.Threading;// Useful way to store info that can be passed as a state on a work itempublic class SomeState{ public int Cookie; public SomeState(int iCookie) { Cookie = iCookie; }}public class Alpha{ public Hashtable HashCount; public ManualResetEvent eventX; public static int iCount = 0; public static int iMaxCount = 0; public Alpha(int MaxCount) { HashCount = new Hashtable(MaxCount); iMaxCount = MaxCount; } // Beta is the method that will be called when the work item is // serviced on the thread pool. // That means this method will be called when the thread pool has // an available thread for the work item. public void Beta(Object state) { // Write out the hashcode and cookie for the current thread Console.WriteLine(" {0} {1} :", Thread.CurrentThread.GetHashCode(), ((SomeState)state).Cookie); // The lock keyword allows thread-safe modification // of variables accessible across multiple threads. Console.WriteLine( "HashCount.Count=={0}, Thread.CurrentThread.GetHashCode()=={1}", HashCount.Count, Thread.CurrentThread.GetHashCode()); lock (HashCount) { if (!HashCount.ContainsKey(Thread.CurrentThread.GetHashCode())) HashCount.Add (Thread.CurrentThread.GetHashCode(), 0); HashCount[Thread.CurrentThread.GetHashCode()] = ((int)HashCount[Thread.CurrentThread.GetHashCode()])+1; } // Do some busy work. // Note: Depending on the speed of your machine, if you // increase this number, the dispersement of the thread // loads should be wider. int iX = 2000; Thread.Sleep(iX); // The Interlocked.Increment method allows thread-safe modification // of variables accessible across multiple threads. Interlocked.Increment(ref iCount); if (iCount == iMaxCount) { Console.WriteLine(); Console.WriteLine("Setting eventX "); eventX.Set(); } }}public class SimplePool{ public static int Main(string[] args) { Console.WriteLine("Thread Pool Sample:"); bool W2K = false; int MaxCount = 10; // Allow a total of 10 threads in the pool // Mark the event as unsignaled. ManualResetEvent eventX = new ManualResetEvent(false); Console.WriteLine("Queuing {0} items to Thread Pool", MaxCount); Alpha oAlpha = new Alpha(MaxCount); // Create the work items. // Make sure the work items have a reference to the signaling event. oAlpha.eventX = eventX; Console.WriteLine("Queue to Thread Pool 0"); try { // Queue the work items, which has the added effect of checking // which OS is running. ThreadPool.QueueUserWorkItem(new WaitCallback(oAlpha.Beta), new SomeState(0)); W2K = true; } catch (NotSupportedException) { Console.WriteLine("These API's may fail when called on a non-Windows 2000 system."); W2K = false; } if (W2K) // If running on an OS which supports the ThreadPool methods. { for (int iItem=1;iItem < MaxCount;iItem++) { // Queue the work items: Console.WriteLine("Queue to Thread Pool {0}", iItem); ThreadPool.QueueUserWorkItem(new WaitCallback(oAlpha.Beta),new SomeState(iItem)); } Console.WriteLine("Waiting for Thread Pool to drain"); // The call to exventX.WaitOne sets the event to wait until // eventX.Set() occurs. // (See oAlpha.Beta). // Wait until event is fired, meaning eventX.Set() was called: eventX.WaitOne(Timeout.Infinite,true); // The WaitOne won't return until the event has been signaled. Console.WriteLine("Thread Pool has been drained (Event fired)"); Console.WriteLine(); Console.WriteLine("Load across threads"); foreach(object o in oAlpha.HashCount.Keys) Console.WriteLine("{0} {1}", o, oAlpha.HashCount[o]); } return 0; }}输出示例注意 下列输出随计算机的不同而不同。 Thread Pool Sample:Queuing 10 items to Thread PoolQueue to Thread Pool 0Queue to Thread Pool 1......Queue to Thread Pool 9Waiting for Thread Pool to drain 98 0 :HashCount.Count==0, Thread.CurrentThread.GetHashCode()==98 100 1 :HashCount.Count==1, Thread.CurrentThread.GetHashCode()==100 98 2 :......Setting eventXThread Pool has been drained (Event fired)Load across threads101 2100 398 4102 1 示例 4：使用 Mutex 对象可以使用 mutex 对象保护共享资源不被多个线程或进程同时访问。mutex 对象的状态或者设置为终止（当它不属于任何线程时），或者设置为非终止（当它属于某个线程时）。同时只能有一个线程拥有一个 mutex 对象。例如，为了防止两个线程同时写入共享内存，每个线程在执行访问该共享内存的代码之前等待 mutex 对象的所属权。写入共享内存后，线程将释放该 mutex 对象。 此示例阐释如何在处理线程过程中使用 Mutex 类、AutoResetEvent 类和 WaitHandle 类。它还阐释在处理 mutex 对象过程中所用的方法。 // Mutex.cs// Mutex object exampleusing System;using System.Threading;public class MutexSample{ static Mutex gM1; static Mutex gM2; const int ITERS = 100; static AutoResetEvent Event1 = new AutoResetEvent(false); static AutoResetEvent Event2 = new AutoResetEvent(false); static AutoResetEvent Event3 = new AutoResetEvent(false); static AutoResetEvent Event4 = new AutoResetEvent(false); public static void Main(String[] args) { Console.WriteLine("Mutex Sample ..."); // Create Mutex initialOwned, with name of "MyMutex". gM1 = new Mutex(true,"MyMutex"); // Create Mutex initialOwned, with no name. gM2 = new Mutex(true); Console.WriteLine(" - Main Owns gM1 and gM2"); AutoResetEvent[] evs = new AutoResetEvent[4]; evs[0] = Event1; // Event for t1 evs[1] = Event2; // Event for t2 evs[2] = Event3; // Event for t3 evs[3] = Event4; // Event for t4 MutexSample tm = new MutexSample( ); Thread t1 = new Thread(new ThreadStart(tm.t1Start)); Thread t2 = new Thread(new ThreadStart(tm.t2Start)); Thread t3 = new Thread(new ThreadStart(tm.t3Start)); Thread t4 = new Thread(new ThreadStart(tm.t4Start)); t1.Start( ); // Does Mutex.WaitAll(Mutex[] of gM1 and gM2) t2.Start( ); // Does Mutex.WaitOne(Mutex gM1) t3.Start( ); // Does Mutex.WaitAny(Mutex[] of gM1 and gM2) t4.Start( ); // Does Mutex.WaitOne(Mutex gM2) Thread.Sleep(2000); Console.WriteLine(" - Main releases gM1"); gM1.ReleaseMutex( ); // t2 and t3 will end and signal Thread.Sleep(1000); Console.WriteLine(" - Main releases gM2"); gM2.ReleaseMutex( ); // t1 and t4 will end and signal // Waiting until all four threads signal that they are done. WaitHandle.WaitAll(evs); Console.WriteLine("... Mutex Sample"); } public void t1Start( ) { Console.WriteLine("t1Start started, Mutex.WaitAll(Mutex[])"); Mutex[] gMs = new Mutex[2]; gMs[0] = gM1; // Create and load an array of Mutex for WaitAll call gMs[1] = gM2; Mutex.WaitAll(gMs); // Waits until both gM1 and gM2 are released Thread.Sleep(2000); Console.WriteLine("t1Start finished, Mutex.WaitAll(Mutex[]) satisfied"); Event1.Set( ); // AutoResetEvent.Set() flagging method is done } public void t2Start( ) { Console.WriteLine("t2Start started, gM1.WaitOne( )"); gM1.WaitOne( ); // Waits until Mutex gM1 is released Console.WriteLine("t2Start finished, gM1.WaitOne( ) satisfied"); Event2.Set( ); // AutoResetEvent.Set() flagging method is done } public void t3Start( ) { Console.WriteLine("t3Start started, Mutex.WaitAny(Mutex[])"); Mutex[] gMs = new Mutex[2]; gMs[0] = gM1; // Create and load an array of Mutex for WaitAny call gMs[1] = gM2; Mutex.WaitAny(gMs); // Waits until either Mutex is released Console.WriteLine("t3Start finished, Mutex.WaitAny(Mutex[])"); Event3.Set( ); // AutoResetEvent.Set() flagging method is done } public void t4Start( ) { Console.WriteLine("t4Start started, gM2.WaitOne( )"); gM2.WaitOne( ); // Waits until Mutex gM2 is released Console.WriteLine("t4Start finished, gM2.WaitOne( )"); Event4.Set( ); // AutoResetEvent.Set() flagging method is done }}示例输出Mutex Sample ... - Main Owns gM1 and gM2t1Start started, Mutex.WaitAll(Mutex[])t2Start started, gM1.WaitOne( )t3Start started, Mutex.WaitAny(Mutex[])t4Start started, gM2.WaitOne( ) - Main releases gM1t2Start finished, gM1.WaitOne( ) satisfiedt3Start finished, Mutex.WaitAny(Mutex[]) - Main releases gM2t1Start finished, Mutex.WaitAll(Mutex[]) satisfiedt4Start finished, gM2.WaitOne( )... Mutex Sample 注意 此示例的输出可能在每台计算机上以及每次运行时均各不相同。运行此示例的计算机的速度及其操作系统都能影响输出的顺序。在多线程环境中，事件可能并不按预期的顺序发生。
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