Parse timespan to DateTime and then use Format ("hh:mm:tt"). For example.
TimeSpan ts = new TimeSpan(16, 00, 00);
DateTime dtTemp = DateTime.ParseExact(ts.ToString(), "HH:mm:ss", CultureInfo.InvariantCulture);
string str = dtTemp.ToString("hh:mm tt");
str will be:
str = "04:00 PM"