主要用到了win32里面的 QueryPerformanceCounter和QueryPerformanceFrequency两个函数

文档链接：https://docs.microsoft.com/zh-cn/windows/win32/api/profileapi/nf-profileapi-queryperformancecounter

 1 class NanoSecondTimer
 2     {
 3       
 4         [DllImport("Kernel32.dll")]
 5         private static extern bool QueryPerformanceCounter(out long lpPerformanceCount);
 6 
 7         [DllImport("Kernel32.dll")]
 8         private static extern bool QueryPerformanceFrequency(out long lpFrequency);
 9 
10         private long startTime, stopTime;
11         private long freq;
12         public NanoSecondTimer()
13         {
14             startTime = 0;
15             stopTime = 0;
16             if (QueryPerformanceFrequency(out freq) == false)
17             {
18                 throw new Win32Exception();
19             }
20         }
21 
22         /// <summary>
23         /// 开始计时
24         /// </summary>
25         public void Start()
26         {
27             Thread.Sleep(0);
28             QueryPerformanceCounter(out startTime);
29         }
30 
31         /// <summary>
32         /// 停止计时
33         /// </summary>
34         public void Stop()
35         {
36             QueryPerformanceCounter(out stopTime);
37         }
38 
39         /// <summary>
40         ///  返回计时器经过时间(单位：秒) 
41         /// </summary>
42         public double Duration
43         {
44             get
45             {
46                 return (double)(stopTime - startTime) / (double)freq;
47             }
48         }
49     }

QueryPerformanceFrequency这个函数会检索性能计数器的频率。性能计数器的频率在系统启动时是固定的，并且在所有处理器上都是一致的。因此，只需在应用初始化时查询频率，即可缓存结果。在运行 Windows XP 或更高版本的系统上，该函数将始终成功，因此永远不会返回零。

下面是测试代码：

1 NanoSecondTimer nanoSecondTimer = new NanoSecondTimer();
2             nanoSecondTimer.Start();
3             for (int i = 0; i < 100000; i++)
4             {
5                 i++;
6             }
7             nanoSecondTimer.Stop();
8             double time = nanoSecondTimer.Duration;