When adding a child LINQ object through its parent object's
collection, this does not mean that the object is immediately available through
the data context. For instance, take a look at the following code.
Customer customer = _context.Customers.First();
Even though the object is added to the customer's orders
collection, the order is not immediately available through the DataContext
object (represented by the "_context" variable). Rather, it is listed
in the ChangeSet object returned from the GetChangeSet() method. The ChangeSet
object contains a collection of the inserted, deleted, and updated objects not
yet submitted to the database, which this orders object is one of them. After
o.ReferenceNumber == "X4590X"));
The order being added is no longer in the change set; it is
not a child of the customer object and readily available in the orders table.