Calculate the interval between two dates

/// <Summary>
/// Calculate the time interval between two dates. The return value is the absolute value of the date difference of the time interval.
/// </Summary>
/// <Param name = "datetime1"> first date and time </param>
/// <Param name = "datetime2"> Second Date and time </param>
/// <Returns> </returns>
Private string datediff (datetime datetime1, datetime datetime2)
{
String datediff = NULL;
Try
{
Timespan ts1 = new timespan (datetime1.ticks );
Timespan ts2 = new timespan (datetime2.ticks );
Timespan Ts = ts1.subtract (ts2). duration ();
Datediff = ts. Days. tostring (); // + "day ";
// + Ts. Hours. tostring () + "hour"
// + Ts. Minutes. tostring () + "Minute"
// + Ts. Seconds. tostring () + "seconds ";
}
Catch
{
Datediff = "";
}
Return datediff;
}