protected void btnLogin_Click(object sender, ImageClickEventArgs e)
        {
            string result = "";
            string idUser = "";

            lblError.Text = "";

            try
            {
                using (QCAstServiceClient serviceRef = new QCAstServiceClient())
                {
                    List <KeyValuePair <string, string> > authenticationResult = serviceRef.AuthenticateUser(txtUserName.Text, txtPassword.Text);
                    result = authenticationResult.Where(p => p.Key == "Result").FirstOrDefault().Value;
                    if (result != "Success")
                    {
                        lblError.Text = result;
                    }
                    else
                    {
                        idUser = authenticationResult.Where(p => p.Key == "IdUser").FirstOrDefault().Value;
                        Session.Add("IdUser", idUser);
                        FormsAuthentication.RedirectFromLoginPage(txtUserName.Text, false);
                    }
                }
            }
            catch (Exception ex)
            {
                NotifyWebmasterOfError("QCAstBilling", "Login", ex.ToString());
                lblError.Text = "Website encountered an error.";
            }
        }