Add hours to datetime but exclude weekends and should be between working hours

Question

I am trying to add hours to a date but want the new date to exclude weekends and only be between 9.00 to 17.00.

example:

first scenario:

if my date is 23/02/2012 16:00:00.
if I add 4 hours to that my new date should be 24/02/2012 12:00:00 (which will be within working hours)

second scenario:

if my date is 24/02/2012 09:00:00 (which is a friday)
if I add 24 hours then the new date should be 27/02/2012 09:00:00 (which would be monday next week at 9am)

so far I got this but am stuck as this will not count for any date that is in past say date passed was 10/02/2012(Friday last week) :

   private static void ExcludeWeekend(Datetime dt)
    {
        DateTime todaysDate = DateTime.Today;
        DateTime dueDate = null;

                if (dueDate.DayOfWeek == DayOfWeek.Friday)
                {
                    dueDate.AddHours(48);
                }
                else if (dueDate.DayOfWeek == DayOfWeek.Saturday)
                {
                    dueDate.AddHours(72);
                }
    }

Answer 1

You can use the class CalendarDateAdd from the Time Period Library for .NET:

// ----------------------------------------------------------------------
public void CalendarDateAddSample()
{
  CalendarDateAdd calendarDateAdd = new CalendarDateAdd();
  // use only weekdays
  calendarDateAdd.AddWorkingWeekDays();
  // setup working hours
  calendarDateAdd.WorkingHours.Add( new HourRange( new Time( 09 ), new Time( 17 ) ) );

  DateTime start = new DateTime( 2012, 2, 23 ); // start date
  TimeSpan offset = new TimeSpan( 4, 0, 0 ); // 4 hours

  DateTime? end = calendarDateAdd.Add( start, offset ); // end date

  Console.WriteLine( "start: {0}", start );
  Console.WriteLine( "offset: {0}", offset );
  Console.WriteLine( "end: {0}", end );
} // CalendarDateAddSample