Check out example codes for "stopwatch c#". It will help you in understanding the concepts better.

Code Example 1

private void timer1_Tick(object sender, EventArgs e)
{
    TimeSpan duration = DateTime.Now - _start;
    label3.Text = duration.ToString(<some format string>);
}

Code Example 2

var timer = new Stopwatch();

  timer.Start();
  // do stuff
  timer.Stop();
}

Learn ReactJs, React Native from akashmittal.com