如何确定用户是使用CrossSlide(手势识别器)向左还是向右滑动?(WP8)

如何确定用户是在执行左swipe还是右？我找到了一个教程，告诉我如何使用CrossSlide Event。我从教程中得到的代码：

Mainpage.xaml：

<Grid Name="LayoutRoot">
    <TextBox Name="TxtGestureNotes"
             Text="Hallo"
             VerticalAlignment="Center"
             HorizontalAlignment="Center">
    </TextBox>
</Grid>

Mainpage.xaml.cs：

public sealed partial class MainPage : Page
{
    GestureRecognizer gestureRecognizer = new GestureRecognizer();
    Windows.UI.Xaml.UIElement element;
    public MainPage()
    {
        this.InitializeComponent();
        Page_Loaded();
    }

    public void GestureInputProcessor(Windows.UI.Input.GestureRecognizer gr, Windows.UI.Xaml.UIElement target) {
        this.gestureRecognizer = gr;
        //Targeted UI element to be performing gestures on it.
        this.element = target;
        //Enable gesture settings for Tap, CrossSlide
        this.gestureRecognizer.GestureSettings = GestureSettings.Tap | GestureSettings.CrossSlide;
        // set up pointer event handlers. these receive input events that are used by the gesture recognizer
        this.element.PointerCanceled += OnPointerCanceled;
        this.element.PointerPressed += OnPointerPressed;
        this.element.PointerReleased += OnPointerReleased;
        this.element.PointerMoved += OnPointerMoved;
        // set up event handlers to respond to gesture recognizer
        gestureRecognizer.Tapped += gestureRecognizer_Tapped;
        //CrossSliding distance thresholds are disabled by default. Use CrossSlideThresholds to set these values.
        Windows.UI.Input.CrossSlideThresholds cst = new Windows.UI.Input.CrossSlideThresholds();
        cst.SelectionStart = 2;
        cst.SpeedBumpStart = 3;
        cst.SpeedBumpEnd = 4;
        cst.RearrangeStart = 5;
        gestureRecognizer.CrossSlideHorizontally = true;
        gestureRecognizer.CrossSlideThresholds = cst;
        gestureRecognizer.CrossSliding += gestureRecognizer_CrossSliding;
    }
    private void Page_Loaded() {
        // For makig gestures operations on Grid named as 'LayoutRoot'
        GestureInputProcessor(gestureRecognizer, LayoutRoot);
    }
    private void Page_Unloaded(object sender, RoutedEventArgs e) {
        // Remove event handlers of gesture recognizers events
        gestureRecognizer.Tapped -= gestureRecognizer_Tapped;
        gestureRecognizer.CrossSliding -= gestureRecognizer_CrossSliding;
    }
    // Pointer Events
    private void OnPointerCanceled(object sender, PointerRoutedEventArgs e) {
        this.gestureRecognizer.CompleteGesture();
        e.Handled = true;
    }
    private void OnPointerPressed(object sender, PointerRoutedEventArgs e) {
        // Route the events to the gesture recognizer
        this.gestureRecognizer.ProcessDownEvent(e.GetCurrentPoint(this.element));
        //Set the pointer capture to the element being interacterd with
        this.element.CapturePointer(e.Pointer);
        // Mark the event handled to prevent execution of default handlers
        e.Handled = true;
    }
    private void OnPointerReleased(object sender, PointerRoutedEventArgs e) {
        this.gestureRecognizer.ProcessUpEvent(e.GetCurrentPoint(this.element));
        e.Handled = true;
    }
    private void OnPointerMoved(object sender, PointerRoutedEventArgs e) {
        this.gestureRecognizer.ProcessMoveEvents(e.GetIntermediatePoints(this.element));
    }
    private void gestureRecognizer_Tapped(GestureRecognizer sender, TappedEventArgs args) {
        TxtGestureNotes.Text = "Tap gesture recognized";
    }
    private void gestureRecognizer_CrossSliding(GestureRecognizer sender, CrossSlidingEventArgs args) {
        TxtGestureNotes.Text = "Slide gesture recognized";
    }

}

但是如何区分滑动手势，例如向右或向左？任何帮助将不胜感激。