[HttpPost]
    [AllowAnonymous]
    [ValidateAntiForgeryToken]
    public IActionResult Register(MyPrivateUsers model)
    {
        if (ModelState.IsValid)
        {
            MyPrivateUsers user = null;
            using (AdminContext db = new AdminContext())
            {
                user = db.MyPrivateUsers.FirstOrDefault(u => u.UserName ==
             model.UserName);
            }

            if (user == null)
            {
                using (AdminContext db = new AdminContext())
                {
                    db.MyPrivateUsers.Add(new MyPrivateUsers { UserName =
            model.UserName, Password = model.Password}); //Добавление в базу
                    db.SaveChanges();

                    user = db.MyPrivateUsers.Where(u => u.UserName ==
         model.UserName).FirstOrDefault(); // Проверка, есть ли юзер в базе.
                }

                if (user != null)
                {
                    return RedirectToAction("Login", "Home");
                }
            }
        }
        return View("Register");

[HttpPost]
    [AllowAnonymous]
    [ValidateAntiForgeryToken]
    public ActionResult Login(LoginModel model, string returnUrl)
    {
        MyPrivateUsers user = null;
        using (AdminContext db = new AdminContext())
        {
            user = db.MyPrivateUsers.Where(u => u.UserName == model.UserName).FirstOrDefault(); // Проверка, есть ли юзер в базе.
        }

        if (user != null)
        {
            WebSecurity.Login(model.UserName, model.Password, persistCookie: model.RememberMe);
            return RedirectToAction("Private", "Home");
        }


        ModelState.AddModelError("", "Ooops");
        return View(model);
    }