如何最快的方式从mysql到asp.net检索数据？

Question

我从mysql检索数据的页面加载速度非常慢

                string cda = "Select * from citymaster where country_code='" + ddl1.SelectedValue + "'";
                MySqlDataAdapter ad = new MySqlDataAdapter(cda, connection);
                DataTable dtb = new DataTable();
                ad.Fill(dtb);

                ddl_city.DataSource = dtb;
                ddl_city.DataTextField = "city_name";
                ddl_city.DataValueField = "city_name";
                ddl_city.DataBind();
                ddl_city.Items.Insert(0, new ListItem("Select City", "0"));
       ```