public async Task<ActionResult> Login(LoginViewModel model, string returnUrl)
        {
            if (!ModelState.IsValid)
            {
                return View(model);
            }

            // 这不会计入到为执行帐户锁定而统计的登录失败次数中
            // 若要在多次输入错误密码的情况下触发帐户锁定,请更改为 shouldLockout: true
            var result = await SignInManager.PasswordSignInAsync(model.Email, model.Password, model.RememberMe, shouldLockout: false);
            switch (result)
            {
                case SignInStatus.Success:
                    return RedirectToLocal(returnUrl);
                case SignInStatus.LockedOut:
                    return View("Lockout");
                case SignInStatus.RequiresVerification:
                    return RedirectToAction("SendCode", new { ReturnUrl = returnUrl, RememberMe = model.RememberMe });
                case SignInStatus.Failure:
                default:
                    ModelState.AddModelError("", "无效的登录尝试。");
                    return View(model);
            }
        }
        public async Task<ActionResult> Login(LoginViewModel model, string returnUrl)
        {
            if (!ModelState.IsValid)
            {
                return View(model);
            }

            // Anmeldefehler werden bezüglich einer Kontosperre nicht gezählt.
            // Wenn Sie aktivieren möchten, dass Kennwortfehler eine Sperre auslösen, ändern Sie in "shouldLockout: true".
            var result = await SignInManager.PasswordSignInAsync(model.Email, model.Password, model.RememberMe, shouldLockout: true);
            switch (result)
            {
                case SignInStatus.Success:
                    return RedirectToLocal(returnUrl);
                case SignInStatus.LockedOut:
                    return View("Lockout");
                case SignInStatus.RequiresVerification:
                    return RedirectToAction("SendCode", new { ReturnUrl = returnUrl, RememberMe = model.RememberMe });
                case SignInStatus.Failure:
                default:
                    ModelState.AddModelError("", "Ungültiger Anmeldeversuch.");
                    return View(model);
            }
        }