void client_GetUserCompleted(object sender, WebService.GetUserCompletedEventArgs e)
 {
     if (e.Result == null)
     {
         NavigationService.Navigate(new Uri("/RegisterPageFacebook.xaml", UriKind.RelativeOrAbsolute));
     }
     else if (e.Result.AccountType != (int)AccountType.Facebook)
     {
         MessageBox.Show("This account is not registered with facebook!");
         NavigationService.Navigate(new Uri("/LoginPage.xaml", UriKind.RelativeOrAbsolute));
     }
     else
     {
         userIdentity.Authenticated += userIdentity_Authenticated;
         userIdentity.FetchARSocialData((string)facebookData["Email"]);
     }
 }