NullReferenceException was unhandled using stored procedures

Question

I cant seem to solve the problem with my code:

public BindingSource getDataSource(string user_name)
    {
        string query = "Select user_name from UserPass_table where user_name Like @user_Name + '%' ;";
        BindingSource bindSource = new BindingSource();
        if (this.connect())
        {
            try
            {
                using (MySqlDataAdapter dA = new MySqlDataAdapter(query, connection))
                {
                    using (DataTable DT = new DataTable())
                    {
                        dA.InsertCommand.Parameters.AddWithValue("@user_Name", user_name);
                        dA.Fill(DT);
                        bindSource.DataSource = DT;
                    }
                }
            }
            catch (MySqlException e)
            {
                MessageBox.Show(e.Number.ToString());
                bindSource.DataSource = null;
            }
        }
        this.close();
        return bindSource;
    }

when I ran this code: it says System.NullReferenceException was unhandled at this line of code

dA.InsertCommand.Parameters.AddWithValue("@user_Name", user_name);