private void BtnSave_Click(object sender, EventArgs e) { SqlConnection conn = DAO.Connection; SqlCommand cmd = conn.CreateCommand(); conn.Open(); // create random and check BusID duplicate string routeID; do { cmd.Parameters.Clear(); routeID = DAO.RandomID(); cmd.CommandText = "SELECT * FROM Routes WHERE RouteID = @id"; cmd.Parameters.AddWithValue("@id", routeID); SqlDataReader reader = cmd.ExecuteReader(); bool exist = reader.Read(); reader.Close(); if (!exist) { break; } } while (true); Route route = new Route(); route.RouteID = routeID; route.FromCityID = cbFromCity.SelectedValue; route.ToCityID = cbToCity.SelectedValue; int duration; if (int.TryParse(txtDuration.Text, out duration)) { route.Duration = duration; RouteDAO.addRoute(route); } else { durationError.Controls.Add(new LiteralControl("<div class='alert alert-danger'>")); Label error = new Label(); error.Text = "Duration must be number !"; durationError.Controls.Add(error); durationError.Controls.Add(new LiteralControl("</div>")); } }