ScrollViewer Zoom/Pan Usage

public partial class MainWindow : Window {
    private ScrollViewerZoomPanHelper zpHelper;
    private ZoomSliderHelper zoomSliderHelper;
    private bool internalUpdate = false;
    public MainWindow() {
        InitializeComponent();
    }

    protected override void OnInitialized(EventArgs e) {
        zoomSliderHelper = new ZoomSliderHelper() {
            ValueRange = new Range<double>(zoomSlider.Minimum, zoomSlider.Maximum),
            ZoomRange = new Range<double>(0.1, 3),
            NumSteps = 20
        };
        zpHelper = new ScrollViewerZoomPanHelper() {
            ScaledElement = (FrameworkElement)colorMapperAndLegend.ColorMapperCtrl.ScaledHolderElement,
            ScrollViewer = colorMapperAndLegend.ScrollViewer,
            MinZoom = zoomSliderHelper.ZoomRange.Min,
            MaxZoom = zoomSliderHelper.ZoomRange.Max,
            ChangePercent = zoomSliderHelper.ZoomStepSize
        };
        zpHelper.ZoomChanged += new System.EventHandler(zpHelper_ZoomChanged);
    }

    private void zpHelper_ZoomChanged(object sender, System.EventArgs e) {
        internalUpdate = true;
        zoomSlider.Value = zoomSliderHelper.ZoomToSlider(zpHelper.Zoom);
        internalUpdate = false;
    }

    private void zoomSlider_ValueChanged(object sender, RoutedPropertyChangedEventArgs<double> e) {
        if (internalUpdate) return;
        zpHelper.Zoom = zoomSliderHelper.SliderToZoom(zoomSlider.Value);
    }
}