Xamarin.Auth Fail on UWP

Question

I made a test with Xamarin.Auth on uwp, I got error System.NullReferenceException: 'Object reference not set to an instance of an object.' with code below:

            var authenticator = new OAuth2Authenticator(
                        "clientid",
                        "client serrect-@:?",
                        "openid profile",
                        new Uri("https://login.microsoftonline.com/common/oauth2/v2.0/authorize"),
                        new Uri("com.microrookie://oauth2redirect"),
                        new Uri("https://login.microsoftonline.com/common/oauth2/v2.0/token"),
                        null,
                        false);
            authenticator.Completed += Authenticator_Completed;
            authenticator.Error += Authenticator_Error;
            //authenticator.GetUI();
            //Frame.Navigate(authenticator.GetUI(), authenticator);
            var presenter = new Xamarin.Auth.Presenters.OAuthLoginPresenter();
            presenter.Login(authenticator); //error throw this line

Answer 1

The null reference is thrown in OAuth2Authenticator.cs for UWP. On Line 790, code calls:

task_scheduler = TaskScheduler.FromCurrentSynchronizationContext();

For UWP this throws an InvalidOperationException (see authors comments in catch handler); since task_scheduler is null, a null reference exception is subsequently thrown.

The fix appears to be simple, juat prefix the offending code with:

if ( SynchronizationContext.Current == null )
    task_scheduler = TaskScheduler.Current;
else ...

I am new to these proceedings, how do I submit my suggestion to the authors?

Answer 2

Xamarin.Auth Fail on UWP

The problem is you have not call AuthenticationConfiguration.Init() method in UWP client app.

......

Xamarin.Forms.Forms.Init(e);
global::Xamarin.Auth.Presenters.UWP.AuthenticationConfiguration.Init();

For redirect Url, please refer official document,

If you are using ADAL to build application for your desktop or mobile devices, you may select from the suggested Redirect urls below.

I have checked your redirect uri scheme (microrookie://auth), if you have resisted protocol for your app, it will launch the app after authentication responses successfully.