计算C#程序执行时间

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);  
} 


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);  
}