MainPage.xaml.cs

        public MobileServiceClient client;
        public MobileServiceUser user;
        public MainPage()
        {
            this.InitializeComponent();
        }

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

            client = new MobileServiceClient("https://uwpstories.azurewebsites.net");
            
        }

        private async void Login_Click(object sender, RoutedEventArgs e)
        {
            Button button = sender as Button;

            try
            {
                switch (button.Content as string)
                {
                    case "Facebook":
                        user = await client.LoginAsync(MobileServiceAuthenticationProvider.Facebook);
                        break;
                    case "Google":
                        user = await client.LoginAsync(MobileServiceAuthenticationProvider.Google);
                        break;
                    case "Microsoft Account":
                        user = await client.LoginAsync(MobileServiceAuthenticationProvider.MicrosoftAccount);
                        break;
                    case "Twitter":
                        user = await client.LoginAsync(MobileServiceAuthenticationProvider.Twitter);
                        break;
                }
            }
            catch (Exception)
            {

            }
            
            if (user != null)
            {
                var userInfo = await client.InvokeApiAsync<UserInfo>("UserInfo",HttpMethod.Get,null);

                userName.Text = userInfo.Name;

                var httpclient = new HttpClient();
                var bytes = await httpclient.GetByteArrayAsync(userInfo.ImageUri);
                var bi = new BitmapImage();
                await
                    bi.SetSourceAsync(
                        new MemoryStream(bytes).AsRandomAccessStream());

                userImage.Source = bi;
            }
        }