W8.1 Live SDK 5.6 - LiveAuthClient.InitializeAsync System.NullReferenceException

问题

I'm developing a Windows 8.1 App (XAML/C#) with MVVM Light.

I used to keep my LiveId inside the code just for debugging, but now it's time to do the LogIn.

Currently i'm stuck with this piece of code:

this.authClient = new LiveAuthClient();
LiveLoginResult loginResult = await this.authClient.InitializeAsync(scopes);

It keeps giving me the error:

An exception of type 'System.NullReferenceException' occurred in mscorlib.dll but was not handled in user code

Additional information: Object reference not set to an instance of an object.

Source Code:

    private static readonly string[] scopes =
            new string[] { 
               "wl.signin", 
               "wl.basic", 
               "wl.offline_access"};

    private LiveAuthClient authClient;
    private LiveConnectClient liveClient;


    public DashboardView()
    {
        this.InitializeComponent();
    }

    protected override void OnNavigatedTo(NavigationEventArgs e)
    {
        base.OnNavigatedTo(e);
        this.InitializePage();
    }

    private async void InitializePage()
    {
        this.authClient = new LiveAuthClient();
        LiveLoginResult loginResult = await this.authClient.InitializeAsync(scopes);
        if (loginResult.Status == LiveConnectSessionStatus.Connected)
        {
            if (this.authClient.CanLogout)
            {
                this.btnLogin.Content = "Sign Out";
            }
            else
            {
                this.btnLogin.Visibility = Visibility.Collapsed;
            }

            this.liveClient = new LiveConnectClient(loginResult.Session);
            this.GetMe();
        }
    }

    private async void btnLogin_Click(object sender, RoutedEventArgs e)
    {
        if (this.btnLogin.Content.ToString() == "Sign In")
        {
            LiveLoginResult loginResult = await this.authClient.LoginAsync(scopes);
            if (loginResult.Status == LiveConnectSessionStatus.Connected)
            {
                if (this.authClient.CanLogout)
                {
                    this.btnLogin.Content = "Sign Out";
                }
                else
                {
                    this.btnLogin.Visibility = Visibility.Collapsed;
                }

                this.liveClient = new LiveConnectClient(loginResult.Session);
                this.GetMe();
            }
        }
        else
        {
            this.authClient.Logout();
            this.btnLogin.Content = "Sign In";
        }
    }

    private async void GetMe()
    {
        Task<LiveOperationResult> task = this.liveClient.GetAsync("me");

        var result = await task;
        dynamic profile = result.Result;
    }

I even tried some different scopes and this was my last try.

Thanks in advance.

回答1:

As far as i have noticed that problem occurred in my case when calling LiveAuthClient.LoginAsync through interface and/or class library. In order to solve the problem I have used mediator Messenger class from MVVMLight library to login from application entry project which is associated with the store. To associate app with the store follow this article http://www.codeproject.com/Articles/708863/Developer-Guide-to-Write-Windows-Store-App-usi .

My view models are in separate (portable) library and they reference contracts library which contains interfaces for services, in order to login without getting NullReferenceException create a message class.

This solution is for WP8.1, but as platforms are sharing same SDK, it should work. In sample code I am using Messenger and SimpleIoc from MVVM light.

Message class:

public class OneDriveLoginRequestMessage
{
    public Action CallbackAction { get; set; }
}

SimpleIoc.Default.Register(() => new OneDriveClient());

Inside App.xaml.cs file in method RootFrame_FirstNavigated add following code to login:

Messenger.Default.Register<OneDriveLoginRequestMessage>(this, async (msg) =>
{
    await SimpleIoc.Default.GetInstance<OneDriveClient>().Login();
    if (msg != null && msg.CallbackAction != null)
    {
        msg.CallbackAction();
    }
});

And finally to login from view model:

private void NavigateToOneDrivePage()
{
    MessengerInstance.Send(new OneDriveLoginRequestMessage
    {
        CallbackAction = async () =>
        {
            // after login continue here...
            var client = SimpleIoc.Default.GetInstance<OneDriveClient>();
        }
    });
}

I hope that solves your problem.

Best, M

来源：https://stackoverflow.com/questions/24779831/w8-1-live-sdk-5-6-liveauthclient-initializeasync-system-nullreferenceexception

标签

winrt-xaml

async-await

windows-8.1

live-sdk