trial.cs

private void PhoneApplicationPage_Loaded(object sender, RoutedEventArgs e)
{
	settings = IsolatedStorageSettings.ApplicationSettings;
	Uri savedpage;
	if (settings.TryGetValue("page", out savedpage))
	{
		 Browser.Source = savedpage;
	}

	if (IsTrialMode())
	{
		 ApplicationBarMenuItem b = new ApplicationBarMenuItem("comprar app");
		 b.Click += BuyButton_Click;

		 ApplicationBar.MenuItems.Add(b);
	}
}

private void BuyButton_Click(object sender, EventArgs e)
{
	var detailTask = new Microsoft.Phone.Tasks.MarketplaceDetailTask();
	detailTask.Show();
}

private bool IsTrialMode()
{
#if DEBUG
	return true;
#else
	var licenseInfo = new Microsoft.Phone.Marketplace.LicenseInformation();
	return licenseInfo.IsTrial();
#endif
}