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// StopWatch.cs
using System;
using System.ComponentModel;
using System.Runtime.InteropServices;
public class StopWatch
{
[DllImport("Kernel32.dll")]
static extern bool QueryPerformanceCounter(out long lpPerformanceCount);
[DllImport("Kernel32.dll")]
static extern bool QueryPerformanceFrequency(out long lpFrequency);
long start;
long stop;
long frequency;
const decimal multiplier = 1.0e9M;
public StopWatch()
{
if (QueryPerformanceFrequency(out frequency) == false)
{
// Frequency not supported
throw new Win32Exception();
}
}
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);
}
}
它的使用比DateTime.Now还要简单，如下所示：
StopWatch myTimer = new StopWatch();
// Measure without boxing
myTimer.Start();
for(int i = 0; i < iterations; i++)
{
// do some work to time
}
myTimer.Stop();
// 计算每次循环所花的平均时间（单位：十亿分之一秒）
double result = myTimer.Duration(iterations);
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