public ActionResult Login(LoginViewModel model)
        {
            Session.Add("loginReturnURL", "/");
            Session.Add("loginUserName", model.UserName);
            if (!ModelState.IsValid)
            {
                return(View(model));
            }

            if (Membership.ValidateUser(model.UserName, model.Password)) // Verify User
            {
                // Duo Authentication
                DuoWebRequest DuoRequest = new DuoWebRequest()           // Create a new Duo Web Request to Send
                {
                    IKEY     = ConfigurationManager.AppSettings["ikey"], // Get Integration Key
                    SKEY     = ConfigurationManager.AppSettings["skey"], // Get DUO Secret Key
                    AKEY     = ConfigurationManager.AppSettings["akey"], // Generate Unique Application Secret Key for DUO
                    USERNAME = model.UserName
                };

                string signRequest = DuoWebAuthentication.DuoWeb_SignRequest(DuoRequest); // Create signed Request for user to DUO

                Session.Add("SignRequest", signRequest);
                return(this.RedirectToAction("DuoAuthentication")); // Send user to Authentication Page For Duo's jQuery code
            }
            return(View(model));                                    // User is invlid just show model
        }