测量程序运行时间

           string a = string.Empty;
            Stopwatch sp = new Stopwatch();//using System.Diagnostics;
            sp.Start();//开始
            for (int i = 0; i < 100000; i++)
            {
                a += i;
            }
            sp.Stop();//结束
            Console.WriteLine(sp.Elapsed);//sp.Elapsed为时间间隔