A StopWatch class can measure elapsed time for one interval.
We can use for measuring performance of the new code blocks or algorithms.

Use IsRunning method to determine the state of StopWatch object.
Use Start method to begin measuring elapsed time, and Stop method to stop measuring elapsed time.

        {
            Stopwatch stopwatch = new Stopwatch();
            stopwatch.Start();
            textBox1.Text = DateTime.Now.TimeOfDay.ToString();
            Application.DoEvents();

            // Perform a long process
            Thread.Sleep(34564);

            stopwatch.Stop();
            textBox2.Text = DateTime.Now.TimeOfDay.ToString();
            textBox3.Text = stopwatch.Elapsed.Milliseconds.ToString();
            Application.DoEvents();
        }

You can find an example application in the attached file.