string conStr = ConfigurationManager.ConnectionStrings["lap_appConnectionString"].ConnectionString;
           using (SqlConnection cnz = new SqlConnection(conStr))
           {
               SqlCommand cmdzs = new SqlCommand("SELECT MAX (patient_id) as max_patient_id FROM patient_data ", cnz);
               cmdzs.CommandType = CommandType.Text;
               cnz.Open();
               max_id_lbl.Text = cmdzs.ExecuteScalar().ToString();
           }