How to Get time interval between 2 times in c#

This blog shows on how to Get time interval between 2 times in c#.

public string GetInterval(string srtTime, string stpTime)
        {
            string Interval;
            startTime = Convert.ToDateTime(srtTime);
            stopTime = Convert.ToDateTime(stpTime);
            processTime = stopTime - startTime;
            Interval = Convert.ToString(processTime);
            return Interval;
        }