[Authorize]
public class AccountController : Controller
{
    private UserService _userService;
    public UserService UserService{
        get { return _userService ?? (_userService = new UserService()); }
    }

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

        //the line with SignInManager is Default in project
        //var result = await SignInManager.PasswordSignInAsync(model.Email, model.Password, model.RememberMe, shouldLockout: false);

        //I have implemented my User service which checks in DB is there exists such a user with email and password and returns the same SignInStatus
        var result = UserService.Authenticate(model.Email, model.Password);

        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("", "Invalid login attempt.");
                return View(model);
        }
    }
}

public class UserService : IUserService
{
    public SignInStatus Authenticate(string email, string password)
    {
        if (string.IsNullOrEmpty(email) || string.IsNullOrEmpty(password))
        {
            return SignInStatus.Failure;
        }

        //TODO: perform authentication against DB account
        if (email == "mymail@mail.com" && password == "123")
        {
            return SignInStatus.Success;
        }
        else
        {
            return SignInStatus.Failure;
        }
    }
}

public class AdministrationController : Controller
{
    // GET: Admin/Admin
    [Authorize]
    public ActionResult Index()
    {
        return View();
    }
}

public class AdministrationController : Controller
{
    // GET: Admin/Admin
    [Authorize(Roles = "Administrator")]
    public ActionResult Index()
    {
        return View();
    }
}

case SignInStatus.Success:
    var user = new ApplicationUser
    {
        Email = model.Email,
        UserName = model.Email,
        ... set any other properties that you find convenient
    };
    await SignInManager.SignInAsync(user, false, false);
    return RedirectToLocal(returnUrl);