Entity Framework attached + detached entities

entityFramework-101.cs

int pkSeqNo = 123;

//detached entity
MyChildEntity  child_entity = new MyChildEntity();

MyParentEntity attachedParentEntity = dbCtx.MyParentEntity
					.Where( h => h.seqNo == pkSeqNo)
					.Include( h => h.MyChildEntity)
					.SingleOrDefault();

										
//version 1: you can get a handle on the added entity...
MyChildEntity inserted = dbCtx.MyChildEntity.Add(child_entity);

//version 2: returns void, no handle to the added entity...
attachedParentEntity.MyChildEntity.Add(child_entity); //NB: the nav prop .MyChildEntity in this line is actually a collection ICollection<MyChildEntity>