public void Delete(int POId)
        {
            QuickReceiptEntities ctx = new QuickReceiptEntities();

            var existingPO = (from p in ctx.PurchaseOrders
                              where p.POId == POId
                              select p).FirstOrDefault();

            if (existingPO == null)
            {
                throw new ObjectNotFoundException("Purchase Order with POId " + POId + "couldn't be found int the database.  No deletion was performed.");
            }

            ctx.DeleteObject(existingPO);
            ctx.SaveChanges();
        }