Question

I have this code:

Schedule s = _entities.Schedules.Where(x => x.ScheduleID == schedule.ScheduleID && x.BookingObject.BookingObjectID == bookingObjectID).FirstOrDefault();

if(s == null)
    s = new Schedule();

s.ScheduleStart = schedule.ScheduleStart;
s.ScheduleEnd = schedule.ScheduleEnd;

foreach (var t in schedule.Timetables)
{   
    s.Timetables.Add(t);
}

_entities.AddToSchedules(s);

_entities.SaveChanges();

Exception: System.InvalidOperationException

the object schedule gets passed in as a parameter

EDIT:

changed to:

  Schedule sh = new Schedule();


  sh.ScheduleStart = schedule.ScheduleStart;
  sh.ScheduleEnd = schedule.ScheduleEnd;

  foreach (var t in schedule.Timetables)
  {
       //sh.Timetables.Add(t);  // doesn't work
        sh.Timetables.Add(new Timetable { DayOfWeek = t.DayOfWeek, StartTime = t.StartTime, EndTime = t.EndTime });   // works
  }

  _entities.AddToSchedules(sh);

  _entities.SaveChanges();

is there some logical reason why sh.Timetables.Add(t) doesn’t work since its a collection of Timetable?

/M

Answer 1

UPDATE: Just confirmed that this is likely to be the reason. And created a new tip in my tips series to explain.

I can think of one possible reason.Is the relationship between schedule.Timetables one to many? I.e. Can a timetable only be assigned to one schedule at a time?

If so, this is failing:

  foreach (var t in schedule.Timetables)  {       
     sh.Timetables.Add(t); 
  }

Because as you add the ‘t’ to a different schedule, it is automatically removed from the old schedule.Timetables collection, which of course modifies the collection you are enumerating, which is a no-no.

If so, the solution is simply to do something like this:

  var timetables = schedule.Timetables.ToArray();
  foreach (var t in timetables)  {       
     sh.Timetables.Add(t); 
  }

Here you enumerate the collection, before you start modifying it.