System.Exception: Registration error

Przy próbie dodania możliwości logowania przez facebooka napotkałem na problem, oto błąd:

Szczegóły wyjątku: System.Exception: Registration error

miejsce wystąpienia błędu:

Wiersz 189:                        throw new Exception("Registration error"); 

oraz cała akcja kontrolera:

   [AllowAnonymous]
        public async Task<ActionResult> ExternalLoginCallback(string returnUrl)
        {
            var loginInfo = await AuthenticationManager.GetExternalLoginInfoAsync();
            if (loginInfo == null)
            {
                return RedirectToAction("Login");
            }

            // Sign in the user with this external login provider if the user already has a login
            var result = await SignInManager.ExternalSignInAsync(loginInfo, isPersistent: false);
            switch (result)
            {
                case SignInStatus.Success:
                    return RedirectToLocal(returnUrl);
                case SignInStatus.Failure:
                default:
                    // If the user does not have an account, create account with external provider login
                    // in reality, we might ask for providing e-mail (+ confirming it)
                    // we also need some error checking logic (ie. verification if user doesn't already exist)

                    var user = new ApplicationUser
                    {
                        UserName = loginInfo.Email,
                        Email = loginInfo.Email,
                        UserData = new UserData { Email = loginInfo.Email }
                    };

                    var registrationResult = await UserManager.CreateAsync(user);
                    if (registrationResult.Succeeded)
                    {
                        registrationResult = await UserManager.AddLoginAsync(user.Id, loginInfo.Login);
                        if (registrationResult.Succeeded)
                        {
                            await SignInManager.SignInAsync(user, isPersistent: false, rememberBrowser: false);
                            return RedirectToLocal(returnUrl);
                        }
                        else
                            throw new Exception("External provider association error");
                    }
                    else
                        throw new Exception("Registration error");
            }
        } 

dodatkowo podaje jeszcze ślad stosu:

[Exception: Registration error]
CookProject.Controllers.<ExternalLoginCallback>d__f.MoveNext() in c:\Users\Jakub\Desktop\CookProject\CookProject\Controllers\AccountController.cs:189
System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) +99
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) +58
System.Runtime.CompilerServices.TaskAwaiter.GetResult() +26
System.Threading.Tasks.TaskHelpersExtensions.ThrowIfFaulted(Task task) +61
System.Web.Mvc.Async.TaskAsyncActionDescriptor.EndExecute(IAsyncResult asyncResult) +114
System.Web.Mvc.Async.<>c__DisplayClass37.<BeginInvokeAsynchronousActionMethod>b__36(IAsyncResult asyncResult) +66
System.Web.Mvc.Async.WrappedAsyncResult1.CallEndDelegate(IAsyncResult asyncResult) +47 System.Web.Mvc.Async.WrappedAsyncResultBase1.End() +136
System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +102
System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult) +49
System.Web.Mvc.Async.AsyncInvocationWithFilters.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3d() +117
System.Web.Mvc.Async.<>c__DisplayClass46.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3f() +323
System.Web.Mvc.Async.<>c__DisplayClass33.<BeginInvokeActionMethodWithFilters>b__32(IAsyncResult asyncResult) +44
System.Web.Mvc.Async.WrappedAsyncResult1.CallEndDelegate(IAsyncResult asyncResult) +47 System.Web.Mvc.Async.WrappedAsyncResultBase1.End() +136
System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +102
System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult) +50
System.Web.Mvc.Async.<>c__DisplayClass2b.<BeginInvokeAction>b__1c() +72
System.Web.Mvc.Async.<>c__DisplayClass21.<BeginInvokeAction>b__1e(IAsyncResult asyncResult) +185
System.Web.Mvc.Async.WrappedAsyncResult1.CallEndDelegate(IAsyncResult asyncResult) +42 System.Web.Mvc.Async.WrappedAsyncResultBase1.End() +133
System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +56
System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) +40
System.Web.Mvc.Controller.<BeginExecuteCore>b__1d(IAsyncResult asyncResult, ExecuteCoreState innerState) +34
System.Web.Mvc.Async.WrappedAsyncVoid1.CallEndDelegate(IAsyncResult asyncResult) +70 System.Web.Mvc.Async.WrappedAsyncResultBase1.End() +133
System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +56
System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +37
System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +44
System.Web.Mvc.Controller.<BeginExecute>b__15(IAsyncResult asyncResult, Controller controller) +39
System.Web.Mvc.Async.WrappedAsyncVoid1.CallEndDelegate(IAsyncResult asyncResult) +62 System.Web.Mvc.Async.WrappedAsyncResultBase1.End() +133
System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +56
System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +37
System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult) +39
System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.EndExecute(IAsyncResult asyncResult) +39
System.Web.Mvc.MvcHandler.<BeginProcessRequest>b__5(IAsyncResult asyncResult, ProcessRequestState innerState) +39
System.Web.Mvc.Async.WrappedAsyncVoid1.CallEndDelegate(IAsyncResult asyncResult) +70 System.Web.Mvc.Async.WrappedAsyncResultBase1.End() +133
System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +56
System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +37
System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +40
System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +38
System.Web.CallHandlerExecutionStep.OnAsyncHandlerCompletion(IAsyncResult ar) +129

czy jest mi ktoś w stanie pomóc?

Zastanawiasz się skąd wziął się wyjątek który sam rzucasz? :>

Wiem że sam wyświetlam wyjątek ale nie wiem skąd się wziął taki błąd

Bo jeśli if (registrationResult.Succeeded) zwraca false czyli jak dobrze rozumiem nie udało się utworzyć użytkownika to rzucasz throw new Exception("Registration error");

rozumiem to tak warunek:
if (registrationResult.Succeeded)
jest false więc:
var registrationResult = await UserManager.CreateAsync(user);
użytkownik nie został utworzony
i rzeczywiście jak sprawdzam wartość loginInfo.Email to jest null

var user = new ApplicationUser
                    {
                        UserName = loginInfo.Email,
                        Email = loginInfo.Email,
                        UserData = new UserData { Email = loginInfo.Email }
                    }; 

więc sprawdzam:
var loginInfo = await AuthenticationManager.GetExternalLoginInfoAsync();
przechodzę do definicji AuthenticationManager
i widzę:

private IAuthenticationManager AuthenticationManager
        {
            get
            {
                return HttpContext.GetOwinContext().Authentication;
            }
        } 

i nie wiem gdzie sprawdzić w którym momencie pojawia się błąd