ManualResetEvent示例

 

2007-05-05 12:34
      在c#多线程里面要用到ManualResetEvent ，从msdn上找到这个示例，可以对此有一个感性认识。
      示例阐释了如何使用等待句柄来发送复杂数字计算的不同阶段的完成信号。此计算的格式为：result = first term + second term + third term，其中每项都要求使用计算出的基数进行预计算和最终计算。

using System;
using System.Threading;

class CalculateTest
{
     static void Main()
     {
         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;
     }
}