public async Task <ActionResult> VerifyCode(string provider, string returnUrl)
        {
            // Require that the user has already logged in via username/password or external login
            if (!await SignInHelper.HasBeenVerified())
            {
                return(View("Error"));
            }
            var user = await UserManager.FindByIdAsync(await SignInHelper.GetVerifiedUserIdAsync());

            if (user != null)
            {
                // To exercise the flow without actually sending codes, uncomment the following line
                // ViewBag.Status = "For DEMO purposes the current " + provider + " code is: " + await UserManager.GenerateTwoFactorTokenAsync(user.Id, provider);
            }
            return(View(new VerifyCodeViewModel {
                Provider = provider, ReturnUrl = returnUrl
            }));
        }