C# 计时程序运行时间

public static void SubTest()
        {
            DateTime beforeDT = System.DateTime.Now;
            int[] a = new int[] { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 };
            //Shuffle(a) is the function you want to test.
            Shuffle(a);
            DateTime afterDT = System.DateTime.Now;
            TimeSpan ts = afterDT.Subtract(beforeDT);
            Console.WriteLine("DateTime costed for Shuffle function is: {0}ms",ts.TotalMilliseconds);
        }

 /// <summary>
        /// 测试for循环优化
        /// </summary>
        /// <returns></returns>
        [HttpGet("test")]
        public ActionResult<ApiResponse> test()
        {
            var result = new ApiResponse();
           Stopwatch sw = new Stopwatch();
           sw.Start();
           //耗时程序

            sw.Stop();
            TimeSpan ts = sw.Elapsed;
            Console.WriteLine("DateTime costed for Shuffle function is: {0}ms", ts.TotalMilliseconds);
            return result;

        }