AutoResetEvent 类
通知正在等待的线程已发生事件。无法继承此类。
AutoResetEvent 允许线程通过发信号互相通信。通常，此通信涉及线程需要独占访问的资源。
线程通过调用 AutoResetEvent 上的 WaitOne 来等待信号。如果 AutoResetEvent 处于非终止状态，则该线程阻塞，并等待当前控制资源的线程通过调用 Set 发出资源可用的信号。
调用 Set 向 AutoResetEvent 发信号以释放等待线程。AutoResetEvent 将保持终止状态，直到一个正在等待的线程被释放，然后自动返回非终止状态。如果没有任何线程在等待，则状态将无限期地保持为终止状态。
可以通过将一个布尔值传递给构造函数来控制 AutoResetEvent 的初始状态，如果初始状态为终止状态，则为 true；否则为 false。
namespace ConsoleApplicationTEST { class Program { static void Main(string[] args) { Calculate calc = new Calculate(); Console.WriteLine("Result = {0}.", calc.Result(234).ToString()); Console.WriteLine("Result = {0}.", calc.Result(55).ToString()); } } class Calculate { double baseNumber, firstTerm, secondTerm, thirdTerm; AutoResetEvent[] autoEvents; ManualResetEvent manualEvent; // Generate random numbers to simulate the actual calculations. Random randomGenerator; public Calculate() { autoEvents = new AutoResetEvent[] { new AutoResetEvent(false), new AutoResetEvent(false), new AutoResetEvent(false) }; manualEvent = new ManualResetEvent(false); } void CalculateBase(object stateInfo) { baseNumber = randomGenerator.NextDouble(); // Signal that baseNumber is ready. manualEvent.Set(); } // The following CalculateX methods all perform the same // series of steps as commented in CalculateFirstTerm. void CalculateFirstTerm(object stateInfo) { // Perform a precalculation. double preCalc = randomGenerator.NextDouble(); // Wait for baseNumber to be calculated. manualEvent.WaitOne(); // Calculate the first term from preCalc and baseNumber. firstTerm = preCalc * baseNumber * randomGenerator.NextDouble(); // Signal that the calculation is finished. autoEvents[0].Set(); } void CalculateSecondTerm(object stateInfo) { double preCalc = randomGenerator.NextDouble(); manualEvent.WaitOne(); secondTerm = preCalc * baseNumber * randomGenerator.NextDouble(); autoEvents[1].Set(); } void CalculateThirdTerm(object stateInfo) { double preCalc = randomGenerator.NextDouble(); manualEvent.WaitOne(); thirdTerm = preCalc * baseNumber * randomGenerator.NextDouble(); autoEvents[2].Set(); } public double Result(int seed) { randomGenerator = new Random(seed); // Simultaneously calculate the terms. ThreadPool.QueueUserWorkItem( new WaitCallback(CalculateBase)); ThreadPool.QueueUserWorkItem( new WaitCallback(CalculateFirstTerm)); ThreadPool.QueueUserWorkItem( new WaitCallback(CalculateSecondTerm)); ThreadPool.QueueUserWorkItem( new WaitCallback(CalculateThirdTerm)); // Wait for all of the terms to be calculated. WaitHandle.WaitAll(autoEvents); // Reset the wait handle for the next calculation. manualEvent.Reset(); return firstTerm + secondTerm + thirdTerm; } } }
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