mobile-windows-universal-dotnet-authenticate-app.md

1. Open the shared project file MainPage.cs and add the following code snippet to the MainPage class:

    // Define a member variable for storing the signed-in user. 
    private MobileServiceUser user;
   
    // Define a method that performs the authentication process
    // using a Facebook sign-in. 
    private async System.Threading.Tasks.Task<bool> AuthenticateAsync()
    {
        string message;
        bool success = false;
        try
        {
            // Change 'MobileService' to the name of your MobileServiceClient instance.
            // Sign-in using Facebook authentication.
            user = await App.MobileService
                .LoginAsync(MobileServiceAuthenticationProvider.Facebook);
            message =
                string.Format("You are now signed in - {0}", user.UserId);
   
            success = true;
        }
        catch (InvalidOperationException)
        {
            message = "You must log in. Login Required";
        }
   
        var dialog = new MessageDialog(message);
        dialog.Commands.Add(new UICommand("OK"));
        await dialog.ShowAsync();
        return success;
    }
   

   This code authenticates the user with a Facebook login. If you are using an identity provider other than Facebook, change the value of MobileServiceAuthenticationProvider above to the value for your provider.

2. Comment-out or delete the call to the RefreshTodoItems method in the existing OnNavigatedTo method override.

   This prevents the data from being loaded before the user is authenticated. Next, you will add a Sign in button to the app that triggers authentication.

3. Add the following code snippet to the MainPage class:

    private async void ButtonLogin_Click(object sender, RoutedEventArgs e)
    {
        // Login the user and then load data from the mobile app.
        if (await AuthenticateAsync())
        {
            // Hide the login button and load items from the mobile app.
            ButtonLogin.Visibility = Windows.UI.Xaml.Visibility.Collapsed;
            //await InitLocalStoreAsync(); //offline sync support.
            await RefreshTodoItems();
        }
    }
   

4. In the Windows Store app project, open the MainPage.xaml project file and add the following Button element just before the element that defines the Save button:

    <Button Name="ButtonLogin" Click="ButtonLogin_Click" 
                    Visibility="Visible">Sign in</Button>
   

5. In the Windows Phone Store app project, add the following Button element in the ContentPanel, after the TextBox element:

    <Button Grid.Row ="1" Grid.Column="1" Name="ButtonLogin" Click="ButtonLogin_Click" 
        Margin="10, 0, 0, 0" Visibility="Visible">Sign in</Button>
   

6. Open the shared App.xaml.cs project file and add the following code:

    protected override void OnActivated(IActivatedEventArgs args)
    {
        // Windows Phone 8.1 requires you to handle the respose from the WebAuthenticationBroker.
        #if WINDOWS_PHONE_APP
        if (args.Kind == ActivationKind.WebAuthenticationBrokerContinuation)
        {
            // Completes the sign-in process started by LoginAsync.
            // Change 'MobileService' to the name of your MobileServiceClient instance. 
            App.MobileService.LoginComplete(args as WebAuthenticationBrokerContinuationEventArgs);
        }
        #endif
   
        base.OnActivated(args);
    }
   

   If the OnActivated method already exists, just add the #if...#endif code block.

7. Press the F5 key to run the Windows Store app, click the Sign in button, and sign into the app with your chosen identity provider.

   When you are successfully logged-in, the app should run without errors, and you should be able to query your backend and make updates to data.
   

8. Right-click the Windows Phone Store app project, click Set as StartUp Project, then repeat the previous step to verify that the Windows Phone Store app also runs correctly.