private void cbmaloai_SelectedIndexChanged(object sender, EventArgs e) { LoaiSanPham lsp = new LoaiSanPham(); lsp.MaLoaiSp = cbmaloai.Text; DataTable dt = loaisanpham_bus.listLoaiSp_SelectMa(lsp); txttenloai.Text = dt.Rows.Count == 0 ? "" : dt.Rows[0][1].ToString(); }