小技巧大智慧：
System.Diagnostics.Stopwatch sw =
new System.Diagnostics.Stopwatch();
sw.Start();
System.Threading.Thread.Sleep( 3000);
sw.Stop();
Console.WriteLine(sw.Elapsed);
sw.Start();
System.Threading.Thread.Sleep( 3000);
sw.Stop();
Console.WriteLine(sw.Elapsed);
