c# - What is the difference between IDbSet.Add and DbEntityEntry.State = EntityState.Added?

Question

In EF 4.1+, is there a difference between these 2 lines of code?

dbContext.SomeEntitySet.Add(entityInstance);
dbContext.Entry(entityInstance).State = EntityState.Added;

Or do they do the same thing? I'm wondering if one might affect child collections / navigation properties differently than the other.

Answer 1

When you use dbContext.SomeEntitySet.Add(entityInstance); the status for this and all its related entities/collections is set to added, while dbContext.Entry(entityInstance).State = EntityState.Added; adds also all the related entities/collections to the context but leaves them as unmodified. So if the entity that you are trying to create has a related entity (and it's value its not null), when you use Add it will create a new object for that child entity, while with the other way it won't.