Dim qqB = (From ugc In dbmBackdrop.Appointments Select ugc).AsQueryable()
                    Dim qq = (From ugc In dbm.Appointments Select ugc).AsQueryable()
                    Dim aptByDlgLis2 = (From a In qq _
                                        Join aB In qqB On aB.ObjectID Equals a.ItemIDNONUNIQUE _
                                        Where a.ByDelegateFrom = currentUserID _
                                        Select aB)
                    Dim aptByDlgList2 = aptByDlgLis2.ToList()

Вот так aptByDlgList2.Count будет больше 0. А вот так

                    Dim qqB = (From ugc In dbmBackdrop.Appointments Select ugc).ToList()
                    Dim qq = (From ugc In dbm.Appointments Select ugc).ToList()
                    Dim aptByDlgLis2 = (From a In qq _
                                        Join aB In qqB On aB.ObjectID Equals a.ItemIDNONUNIQUE _
                                        Where a.ByDelegateFrom = currentUserID _
                                        Select aB)
                    Dim aptByDlgList2 = aptByDlgLis2.ToList()

он будет 0.


И так

                    Dim aptByDlgLis2 = (From a In dbm.Appointments _
                                        Join aB In dbmBackdrop.Appointments On aB.ObjectID Equals a.ItemIDNONUNIQUE _
                                        Where a.ByDelegateFrom = currentUserID _
                                        Select aB)
                    Dim aptByDlgList2 = aptByDlgLis2.ToList()

тоже 0. Почему?