protected void SearchCustomerB_Click(object sender, EventArgs e) { BlUser user = (BlUser)Session["user"]; //get input values string searchBys = SearchBy.Items[SearchBy.SelectedIndex].Value; string value = serchedValue.Text; //get data DataTable customers = user.CustomersSearch($"(Users.{searchBys}='{value}')"); bool isExist = BindTable(customers, CustomersTable); ErCustomer.Text = !isExist ? "Not valid search value" : "";//error massage }