private void detach_ChiTietHoaDons(ChiTietHoaDon entity)
 {
     this.SendPropertyChanging();
     entity.hoadon = null;
 }
 private void attach_ChiTietHoaDons(ChiTietHoaDon entity)
 {
     this.SendPropertyChanging();
     entity.sach = this;
 }
 partial void UpdateChiTietHoaDon(ChiTietHoaDon instance);
 partial void DeleteChiTietHoaDon(ChiTietHoaDon instance);
 partial void InsertChiTietHoaDon(ChiTietHoaDon instance);