var pWorkCellList = from pg in pEntity.FM_WORK_CELL
                                where pg.WorkCellID != strWorkCellID && pg.ParentWorkCellID == null
                                && !(from o in pEntity.FM_WORK_CELL
                                     where o.ParentWorkCellID != null
 

                                     select o.ParentWorkCellID).Contains(pg.WorkCellID)
                                orderby pg.WorkCellID descending
                                select pg;
            return pWorkCellList;

Linq not in 寫法