public void delay(long delay_Time)
        {

            long stop_Value = 0;
            long start_Value = 0;
            long freq = 0;
            long n = 0;
            System.Diagnostics.Stopwatch sw = new System.Diagnostics.Stopwatch();
            QueryPerformanceFrequency(ref freq);  //获取CPU频率
            long count = delay_Time * freq / 1000000; //us级
            QueryPerformanceCounter(ref start_Value); //获取初始前值

            while (n < count) //不能精确判定
            {
                QueryPerformanceCounter(ref stop_Value);//获取终止变量值         
                n = stop_Value - start_Value;
            }      
        }
      .
      .
      .
delay(150);
      本来是想定的150us，结果得出实际时间差不多250左右，而且还很不稳定。不知道什么原因！
希望大大能解惑下！