private void LoginBtn_Click(Object sender, System.EventArgs e)
        {
            // modified by Jonathan Fong
            // www.gt.com.au
            string id = null;

            if (LDAPCheckBox.Checked && GroupList.SelectedValue != "Default")
            {
                string dn = "cn=" + email.Text + "," + GroupList.SelectedValue;
                LDAPHelper.SignOn(dn, password.Text, RememberCheckBox.Checked, null);
            }
            else
            {
                id = PortalSecurity.SignOn(email.Text, password.Text, RememberCheckBox.Checked);
            }

            if (id == null)
            {
                Message.Text    = "Login failed";
                Message.TextKey = "LOGIN_FAILED";
            }
        }