C#计算一段代码运行的时间（三种方法）

第一种方法利用System.DateTime.Now

static void SubTest()  
{  
    DateTime beforDT = System.DateTime.Now;    
  
    //耗时巨大的代码  
      
    DateTime afterDT = System.DateTime.Now;  
    TimeSpan ts = afterDT.Subtract(beforDT);  
    Console.WriteLine("DateTime总共花费{0}ms.", ts.TotalMilliseconds);  
}  

第二种用Stopwatch类(System.Diagnostics)

static void SubTest()  
{  
    Stopwatch sw = new Stopwatch();  
    sw.Start();  
    
    //耗时巨大的代码  
      
    sw.Stop();  
    TimeSpan ts2 = sw.Elapsed;  
    Console.WriteLine("Stopwatch总共花费{0}ms.", ts2.TotalMilliseconds);  
}  

第三种用API实现：

[System.Runtime.InteropServices.DllImport("Kernel32.dll")]  
static extern bool QueryPerformanceCounter(ref long count);  
[System.Runtime.InteropServices.DllImport("Kernel32.dll")]  
static extern bool QueryPerformanceFrequency(ref long count);     
static void SubTest()  
{  
    long count = 0;  
    long count1 = 0;  
    long freq = 0;  
    double result = 0;  
    QueryPerformanceFrequency(ref freq);  
    QueryPerformanceCounter(ref count);     
  
    //耗时巨大的代码  
      
    QueryPerformanceCounter(ref count1);  
    count = count1 - count;  
    result = (double)(count) / (double)freq;  
    Console.WriteLine("QueryPerformanceCounter耗时: {0} 秒", result);  
}