/**
     * Register notification. 
     */
    private string registerNotification(Promotion promotion)
    {
        string notificationRegistractionMessage = "";
        if (Request.IsAuthenticated)
        {
            //register notification
            NotificationManager notificationManager = new NotificationManager(promotion);
            TransactionResponse saveNotifResult = notificationManager.addNotificationForPromotion(Membership.GetUser());
            if (!saveNotifResult.isSuccessful())
            {
                notificationRegistractionMessage = saveNotifResult.getMessage() + saveNotifResult.getErrorCode();
            }
        }

        //IF user is not authenticated - thise should not happen!!
        else
        {
            notificationRegistractionMessage = DBOperationErrorConstants.M_CAN_NOT_AUTHENTICATE_THE_CURRENT_USER
                + DBOperationErrorConstants.M_CAN_NOT_IDENTIFY_CURRENT_USER;
        }
        return notificationRegistractionMessage;
    }