EF4 Saving an Object adds a new child

Question

This is entity framework 4.

CurrentProperty.FMVHistories.Add(FMVPresenter.GetFMVHistoryObject());
DataLayer.AccrualTrackingEntities repository = new AccrualTrackingEntities();
repository.Properties.AddObject(CurrentProperty);
repository.SaveChanges();

Right before I call SaveChanges, CurrentProperty has 1 object in its FMVHistories collection, as it should. Right after the save, it has two - the second of which appears to be a copy of the first, both of which have their foreign keys set, properly.

All objects involved here are new. None were loaded in any way.

FMVHistory has a composite key of 3 fields, one of which is the foreign key to the property it's attached to.

Does anyone know why this second FMVHistory object is getting added?

Answer 1

It looks like this was related to how EF was handling dates. The designer of the FMVHistory table made it with a composite key, part of which was a date field. For some reason when EF put in the object, it truncated the seconds and such from the date it inserted, which broke a lot of weird stuff. I ended up killing the composite key and putting in an identity, and everything is great now.