Reusing authentication token in azure mobile services

MainPage.xaml

    <Grid Background="{StaticResource ApplicationPageBackgroundThemeBrush}">
        <Grid.RowDefinitions>
            <RowDefinition Height="100"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="*"/>
        </Grid.ColumnDefinitions>
        <Button Name="btnLogin" Content="Log in" Margin="10" FontSize="30"
                HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Click="btnLogin_Click" />
        <Button Name="btnReuseToken" Content="Reuse token" Margin="10" FontSize="30" Grid.Column="1"
                HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Click="btnReuseToken_Click" />
        <TextBox Grid.Row="1" Margin="10" Name="txtDebug" Grid.ColumnSpan="2" AcceptsReturn="True" />
    </Grid>

MainPage.xaml.cs

    public sealed partial class MainPage : Page
    {
        public static MobileServiceClient MobileService = new MobileServiceClient(
            "https://blog20131216.azure-mobile.net/",
            "your-app-key-here"
        );

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

        /// <summary>
        /// Invoked when this page is about to be displayed in a Frame.
        /// </summary>
        /// <param name="e">Event data that describes how this page was reached.  The Parameter
        /// property is typically used to configure the page.</param>
        protected override void OnNavigatedTo(NavigationEventArgs e)
        {
        }

        private async void btnLogin_Click(object sender, RoutedEventArgs e)
        {
            try
            {
                var user = await MobileService.LoginAsync(MobileServiceAuthenticationProvider.Facebook);
                this.AddToDebug("Logged in as {0}", user.UserId);
                Windows.Storage.ApplicationData.Current.LocalSettings.Values["userid"] = user.UserId;
                Windows.Storage.ApplicationData.Current.LocalSettings.Values["token"] = user.MobileServiceAuthenticationToken;
                var result = await MobileService.InvokeApiAsync("identities", HttpMethod.Get, null);
                this.AddToDebug("API result: {0}", result);
                MobileService.Logout();
            }
            catch (Exception ex)
            {
                this.AddToDebug("Error: {0}", ex);
            }
        }

        private async void btnReuseToken_Click(object sender, RoutedEventArgs e)
        {
            try
            {
                var userid = Windows.Storage.ApplicationData.Current.LocalSettings.Values["userid"] as string;
                var token = Windows.Storage.ApplicationData.Current.LocalSettings.Values["token"] as string;
                var user = new MobileServiceUser(userid);
                user.MobileServiceAuthenticationToken = token;
                MobileService.CurrentUser = user;
                this.AddToDebug("Logged in (via cached token) as {0}", user.UserId);
                var result = await MobileService.InvokeApiAsync("identities", HttpMethod.Get, null);
                this.AddToDebug("API result: {0}", result);
                MobileService.Logout();
            }
            catch (Exception ex)
            {
                this.AddToDebug("Error: {0}", ex);
            }
        }

        private void AddToDebug(string text, params object[] args)
        {
            if (args != null && args.Length > 0) text = string.Format(text, args);
            this.txtDebug.Text = this.txtDebug.Text + text + Environment.NewLine;
        }
    }