.NET 4 System.Threading.Barrier 类

在Visual Studio 2010 and .NET Framework 4 Training Kit中有个System.Threading.Barrier的Demo，通过Barrier Class我们可以控制线程的运行，做到线程同步的效果。

Barrier Class在使用上十分的简单，只要在Barrier的构造函数中传入participantCount(简单的说就是要等待的线程个数)，并在要同步的点调用SignalAndWait方法就可以了。线程会在调用SignalAndWait之后暂停运行，等待所有参与的线程都到达了同步点才继续往下运行。

举个例子来看，假设今天Charlie、Mac、Dennis三个人相约要去西雅图喝咖啡。由于三个人的住的地区不尽相同，且车子都需要加油，因此他们约在途中会经过的加油站待会合后一同前往。这样的情境我们可以通过Thread与Barrier用程序仿真出来。

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading; namespace BarrierDemo { class Program { static Barrier sync; static CancellationToken token; static void Main(string[] args) { var source = new CancellationTokenSource(); token = source.Token; sync = new Barrier(3); var charlie = new Thread(() => DriveToBoston("Charlie", TimeSpan.FromSeconds(1))); charlie.Start(); var mac = new Thread(() => DriveToBoston("Mac", TimeSpan.FromSeconds(2))); mac.Start(); var dennis = new Thread(() => DriveToBoston("Dennis", TimeSpan.FromSeconds(3))); dennis.Start(); //source.Cancel(); charlie.Join(); mac.Join(); dennis.Join(); Console.ReadKey(); } static void DriveToBoston(string name, TimeSpan timeToGasStation) { try { Console.WriteLine("[{0}] Leaving House", name); // Perform some work Thread.Sleep(timeToGasStation); Console.WriteLine("[{0}] Arrived at Gas Station", name); // Need to sync here sync.SignalAndWait(token); // Perform some more work Console.WriteLine("[{0}] Leaving for Boston", name); } catch (OperationCanceledException) { Console.WriteLine("[{0}] Caravan was cancelled! Going home!", name); } } } }

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