getting user_code as null value

guys I have to gety user_code of user. here is my code:
I am getting db= null ...
I am not getting any error message..kindly see code and suggest, whether code has some mistake or code is in proper place???
code: 1st page:
public partial class Login : System.Web.UI.Page { // getting user_code value of user private string GetData(string strUsername)    {        string MyConString = "datasource=localhost;port=3306;username=root;password=ft";        using (MySqlConnection connection = new MySqlConnection(MyConString))        {            connection.Open();            string query = string.Concat("SELECT user_code from  user Where user ...