高精度计数 .net 1.1

.net 2.0中存在一个高精度的计数器StopWartch,
但.net 1.1中却不存在这个计数，可以使用Win32API来模拟这个类，如下：

public class StopWatch
  {
   [DllImport("KERNEL32")]
   private static extern bool QueryPerformanceCounter(
    out long lpPerformanceCount);

   [DllImport("Kernel32.dll")]
   private static extern bool QueryPerformanceFrequency(out long lpFrequency);

   private long start;
   private long stop;
   private long frequency;
   Decimal multiplier = new Decimal(1.0e9);

   public StopWatch()
   {
    if (QueryPerformanceFrequency(out frequency) == false)
    {
     throw new Exception("Frequency not supported");
    }
   }

   public void Start()
   {
    QueryPerformanceCounter(out start);
   }

   public void Stop()
   {
    QueryPerformanceCounter(out stop);
   }

   public double Duration(int iterations)
   {
    return ((((double)(stop - start)* (double) multiplier) / (double) frequency)/iterations);
   }
  }