Добавление роли пользователю ASP.NET Identity

При регистрации в AccountController пытаюсь добавить роль пользователю, однако вылетает такая ошибка (картинка снизу). Делал по примеру и как там заявлено, всё должно работать. Вообще идея в том, чтобы просто приходило имя роли, проверялась на существование и прикреплялась к пользователю. Как в данной ситуации связан _userManager и RoleManager(который doesn't exist)? Ну и соответственно как разрешить данную проблему?

Код AccountController:

[Authorize]
public class AccountController : MvcControllerBase
{
    private ApplicationDbContext context;
    // The Authorize Action is the end point which gets called when you access any
    // protected Web API. If the user is not logged in then they will be redirected to 
    // the Login page. After a successful login you can call a Web API.
    public AccountController(ApplicationUserManager userManager, ApplicationSignInManager signInManager,
        IAuthenticationManager authenticationManager, ApplicationRoleManager roleManager) 
        : base(userManager, signInManager, authenticationManager, roleManager)
    {
        context = new ApplicationDbContext();
    }
    [HttpGet]
    public ActionResult Authorize()
    {
        var claims = new ClaimsPrincipal(User).Claims.ToArray();
        var identity = new ClaimsIdentity(claims, "Bearer");
        _authenticationManager.SignIn(identity);
        return new EmptyResult();
    }
    //
    // GET: /Account/Login
    [AllowAnonymous]
    public ActionResult Login(string returnUrl)
    {
        ViewBag.ReturnUrl = returnUrl;
        return View();
    }
    //
    // POST: /Account/Login
    [HttpPost]
    [AllowAnonymous]
    [ValidateAntiForgeryToken]
    public async Task<ActionResult> Login(LoginViewModel model, string returnUrl)
    {
        if (!ModelState.IsValid)
        {
            return View(model);
        }
        // This doesn't count login failures towards account lockout
        // To enable password failures to trigger account lockout, change to 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("", "Invalid login attempt.");
                return View(model);
        }
    }
    //
    // GET: /Account/VerifyCode
    [AllowAnonymous]
    public async Task<ActionResult> VerifyCode(string provider, string returnUrl, bool rememberMe)
    {
        // Require that the user has already logged in via username/password or external login
        if (!await _signInManager.HasBeenVerifiedAsync())
        {
            return View("Error");
        }
        return View(new VerifyCodeViewModel { Provider = provider, ReturnUrl = returnUrl, RememberMe = rememberMe });
    }
    //
    // POST: /Account/VerifyCode
    [HttpPost]
    [AllowAnonymous]
    [ValidateAntiForgeryToken]
    public async Task<ActionResult> VerifyCode(VerifyCodeViewModel model)
    {
        if (!ModelState.IsValid)
        {
            return View(model);
        }
        // The following code protects for brute force attacks against the two factor codes. 
        // If a user enters incorrect codes for a specified amount of time then the user account 
        // will be locked out for a specified amount of time. 
        // You can configure the account lockout settings in IdentityConfig
        var result = await _signInManager.TwoFactorSignInAsync(model.Provider, model.Code, isPersistent: model.RememberMe, rememberBrowser: model.RememberBrowser);
        switch (result)
        {
            case SignInStatus.Success:
                return RedirectToLocal(model.ReturnUrl);
            case SignInStatus.LockedOut:
                return View("Lockout");
            case SignInStatus.Failure:
            default:
                ModelState.AddModelError("", "Invalid code.");
                return View(model);
        }
    }
    //
    // GET: /Account/Register
    [AllowAnonymous]
    public ActionResult Register()
    {
        return View();
    }
    //
    // POST: /Account/Register
    [HttpPost]
    [AllowAnonymous]
    [ValidateAntiForgeryToken]
    public async Task<ActionResult> Register(RegisterViewModel model)
    {
        if (ModelState.IsValid)
        {
            var user = new ApplicationUser { UserName = model.Email, Email = model.Email, Hometown = model.Hometown};
            var result = await _userManager.CreateAsync(user, model.Password);
            if (result.Succeeded)
            {
                await _signInManager.SignInAsync(user, isPersistent: false, rememberBrowser: false);
                // For more information on how to enable account confirmation and password reset please visit http://go.microsoft.com/fwlink/?LinkID=320771
                // Send an email with this link
                // string code = await UserManager.GenerateEmailConfirmationTokenAsync(user.Id);
                // var callbackUrl = Url.Action("ConfirmEmail", "Account", new { userId = user.Id, code = code }, protocol: Request.Url.Scheme);
                // await UserManager.SendEmailAsync(user.Id, "Confirm your account", "Please confirm your account by clicking <a href=\"" + callbackUrl + "\">here</a>");
                await this._userManager.AddToRoleAsync(user.Id, model.RoleName);
                return RedirectToAction("Index", "Home");
            }
            AddErrors(result);
        }
        // If we got this far, something failed, redisplay form
        return View(model);
    }

Ошибка возникает в "POST: /Account/Register", ну строка по картинке понятна.