public void DeleteSupplierStationeryById(int id)
        {
            SupplierStationery supplierstationery = GetSupplierStationeryById(id);

            supplierstationery.InventoryItem = null;
            supplierstationery.Supplier      = null;
            adProjContext.Remove(supplierstationery);
            adProjContext.SaveChanges();
        }