public ViewResult Register(UserRegistrationModel model,string returnUrl)
        {
            if (ModelState.IsValid)
            {
                var existUser = _repository.Users.FirstOrDefault(item => item.Username.ToLower() == model.Username.ToLower());
                if (existUser == null)
                {
                    var user = new User {Username = model.Username, Password = model.Password, Email = model.Email};

                    _repository.SaveUser(user);

                    ViewBag.returnUrl = returnUrl;
                    return View("RegistrationCompleted");
                }

                ModelState.AddModelError("", "An User with same User name already exists");

                return View(model);
            }
            //
            // If we got this far, something failed, redisplay form!
            //
            return View(model);
        }
        public ActionResult Register(string returnUrl)
        {
            var registerUser = new UserRegistrationModel();

            return View(registerUser);
        }