private void DetachFromVisualTree()
{
// remove the view finder display panel's visual brush and adorner
_viewFinderDisplay = null;
}
private void AttachToVisualTree()
{
// detach from the old tree
DetachFromVisualTree();
// set a reference to the ViewFinder element, if present
SetValue(ViewFinderPropertyKey, Template.FindName("ViewFinder", this) as FrameworkElement);
// locate the view finder display panel
_viewFinderDisplay = VisualTreeHelperEx.FindDescendantByType(this, typeof(ViewFinderDisplay)) as ViewFinderDisplay;
// if a ViewFinder was specified but no display panel is present, throw an exception
if (ViewFinder != null && _viewFinderDisplay == null)
throw new Exception("ZoomControlHasViewFinderButNotDisplay");
// set up the VisualBrush and adorner for the display panel
if (_viewFinderDisplay != null)
{
// create VisualBrush for the view finder display panel
CreateVisualBrushForViewFinder(Content as Visual);
_viewFinderDisplay.Background = this.Background;
// hook up event handlers for dragging and resizing the viewport
_viewFinderDisplay.MouseMove += ViewFinderDisplayMouseMove;
_viewFinderDisplay.MouseLeftButtonDown += ViewFinderDisplayBeginCapture;
_viewFinderDisplay.MouseLeftButtonUp += ViewFinderDisplayEndCapture;
}
}