void FrmHangHoaDanhMuc_Load(object sender, EventArgs e)
 {
     tlDanhMuc.DataSource = busDanhMuc.GetAll();
     if (tlDanhMuc.AllNodesCount > 0)
     {
         category cat = (category)tlDanhMuc.GetDataRecordByNode(tlDanhMuc.Nodes[0]);
         dgvHangHoa.DataSource = busHangHoa.GetByCat(cat);
     }
 }
        private void lkDanhMucSP_EditValueChanged(object sender, EventArgs e)
        {
            if (lkDanhMucSP.EditValue == null)
            {
                return;
            }
            category cat = (category)lkDanhMucSP.GetSelectedDataRow();

            dgvSanPham.DataSource = busHangHoa.GetByCat(cat);
        }