C#计算一段程序运行时间的三种方法

直接代码：

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);
}