Utilizando o modo trial de aplicações no Windows Phone

<!--ContentPanel - place additional content here-->
<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
  <StackPanel Width="450" Height="500">
    <TextBlock Name="lblNomeJogo" Text="Game Windows" FontSize="50"
    TextAlignment="Center" />
    <StackPanel Width="450" Orientation="Horizontal">
      <Button Width="150" Height="100" Name="btnFaseUm" Content="01" />
      <Button Width="150" Height="100" Name="btnFaseDois" Content="02" />
      <Button Width="150" Height="100" Name="btnFaseTres" Content="03" />
    </StackPanel>
    <Button Width="450" Height="100" Name="btnComprar"
    Content="Comprar versão completa" />
  </StackPanel>
</Grid>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Navigation;
using System.Windows.Shapes;
using Microsoft.Phone.Controls;
using Microsoft.Phone.Shell;
using Microsoft.Phone.Marketplace;

namespace TesteApplication
{
    public partial class App : Application
    {
        /// <summary>
        /// Provides easy access to the root frame of the Phone Application.
        /// </summary>
        /// <returns>The root frame of the Phone Application.</returns>
        public PhoneApplicationFrame RootFrame { get; private set; }
        public static LicenseInformation _licenca = new LicenseInformation();
        public static bool IsTrial { get; set; }
        /// <summary>
        /// Constructor for the Application object.
        /// </summary>
        public App()
        {
            // Global handler for uncaught exceptions. 
            UnhandledException += Application_UnhandledException;

            // Standard Silverlight initialization
            InitializeComponent();

            // Phone-specific initialization
            InitializePhoneApplication();

            // Show graphics profiling information while debugging.
            if (System.Diagnostics.Debugger.IsAttached)
            {
                // Display the current frame rate counters.
                Application.Current.Host.Settings.EnableFrameRateCounter = true;

                /* Show the areas of the app that are being redrawn in each
frame.*/
                //Application.Current.Host.Settings.EnableRedrawRegions = true;

                // Enable non-production analysis visualization mode, 
                /* which shows areas of a page that are handed off to GPU
with a colored overlay.*/
                /*Application.Current.Host.Settings.EnableCacheVisualization =
 true;*/

                /* Disable the application idle detection by setting the
 UserIdleDetectionMode property of the*/
                // application's PhoneApplicationService object to Disabled.
                /* Caution:- Use this under debug mode only. Application that 
disables user idle detection will continue to run*/
                /* and consume battery power when the user is not using
the phone.*/
                PhoneApplicationService.Current.UserIdleDetectionMode =
 IdleDetectionMode.Disabled;
            }

        }

        // Code to execute when the application is launching (eg, from Start)
        // This code will not execute when the application is reactivated
        private void Application_Launching(object sender, LaunchingEventArgs e)
        {
            this.VerificarLicenca();
        }

        /* Code to execute when the application is activated (brought to
foreground)*/
        // This code will not execute when the application is first launched
        private void Application_Activated(object sender, ActivatedEventArgs e)
        {
            this.VerificarLicenca();
        }

        /* Code to execute when the application is deactivated
(sent to background)*/
        // This code will not execute when the application is closing
        private void Application_Deactivated(object sender,
DeactivatedEventArgs e)
        {            
        }

        /* Code to execute when the application is closing
(eg, user hit Back)
        This code will not execute when the application is deactivated*/
        private void Application_Closing(object sender, ClosingEventArgs e)
        {
        }

        // Code to execute if a navigation fails
        private void RootFrame_NavigationFailed(object sender,
 NavigationFailedEventArgs e)
        {
            if (System.Diagnostics.Debugger.IsAttached)
            {
                // A navigation has failed; break into the debugger
                System.Diagnostics.Debugger.Break();
            }
        }

        // Code to execute on Unhandled Exceptions
        private void Application_UnhandledException(object sender, 
ApplicationUnhandledExceptionEventArgs e)
        {
            if (System.Diagnostics.Debugger.IsAttached)
            {
                /* An unhandled exception has occurred; break into the
 debugger*/
                System.Diagnostics.Debugger.Break();
            }
        }

        private void VerificarLicenca()
        {
#if DEBUG
            string mensagem = "Nesse exemplo está sendo simulado a "+
 "implementação de um aplicativo Demo. Clique em Ok para simular o modo " +
"de teste, ou Cancel para utilizar a aplicação completa.";
            MessageBoxResult resultado = MessageBox.Show(mensagem, "Debug", 
MessageBoxButton.OKCancel);
            if (resultado == MessageBoxResult.OK)
            {
                IsTrial = true;
            }
            else
            {
                IsTrial = false;
            }
#else
            IsTrial = _license.IsTrial();
#endif

        }

        #region Phone application initialization

        // Avoid double-initialization
        private bool phoneApplicationInitialized = false;

        // Do not add any additional code to this method
        private void InitializePhoneApplication()
        {
            if (phoneApplicationInitialized)
                return;

            /* Create the frame but don't set it as RootVisual yet;
this allows the splash*/
            /* screen to remain active until the application is ready
 to render.*/
            RootFrame = new PhoneApplicationFrame();
            RootFrame.Navigated += CompleteInitializePhoneApplication;

            // Handle navigation failures
            RootFrame.NavigationFailed += RootFrame_NavigationFailed;

            // Ensure we don't initialize again
            phoneApplicationInitialized = true;
        }

        // Do not add any additional code to this method
        private void CompleteInitializePhoneApplication(object sender, 
NavigationEventArgs e)
        {
            // Set the root visual to allow the application to render
            if (RootVisual != RootFrame)
                RootVisual = RootFrame;

            // Remove this handler since it is no longer needed
            RootFrame.Navigated -= CompleteInitializePhoneApplication;
        }

        #endregion
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using Microsoft.Phone.Controls;
using Microsoft.Phone.Tasks;

namespace TesteApplication
{
    public partial class MainPage : PhoneApplicationPage
    {
        // Constructor
        public MainPage()
        {
            InitializeComponent();
        }
        protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
        {
            base.OnNavigatedTo(e);
            if (App.IsTrial)
            {
                btnComprar.Visibility = System.Windows.Visibility.Visible;
                btnFaseDois.IsEnabled = false;
                btnFaseTres.IsEnabled = false;
            }
            else
            {
                btnComprar.Visibility = System.Windows.Visibility.Collapsed;
                btnFaseDois.IsEnabled = true;
                btnFaseTres.IsEnabled = true;
            }
        }

        private void btnComprar_Tap(object sender, GestureEventArgs e)
        {
            MarketplaceDetailTask task = new MarketplaceDetailTask();
            task.Show();
        }

    }
}