private static void CreateDragAdorner()
{
DataTemplate template = GetDragAdornerTemplate(_dragInfo.VisualSource);
if (template == null)
return;
var parentWindow = _dragInfo.VisualSource.GetVisualAncestor<Window>();
UIElement rootElement = null;
UIElement adornment = null;
if (parentWindow != null)
rootElement = parentWindow.Content as UIElement;
if (rootElement == null)
rootElement = (UIElement)Application.Current.MainWindow.Content;
if (_dragInfo.Data is IEnumerable && !(_dragInfo.Data is string))
{
if (((IEnumerable)_dragInfo.Data).Cast<object>().Count() <= 10)
{
var itemsControl = new ItemsControl();
itemsControl.ItemsSource = (IEnumerable)_dragInfo.Data;
itemsControl.ItemTemplate = template;
var border = new Border();
border.Child = itemsControl;
adornment = border;
}
}
else
{
var contentPresenter = new ContentPresenter();
contentPresenter.Content = _dragInfo.Data;
contentPresenter.ContentTemplate = template;
adornment = contentPresenter;
}
if (adornment == null)
return;
adornment.Opacity = 0.5;
DragAdorner = new DragAdorner(rootElement, adornment);
}
private static void DropTarget_PreviewDragOver(object sender, DragEventArgs e)
{
var itemsControl = sender as ItemsControl;
var dropInfo = new DropInfo(sender, e, _dragInfo);
IDropTarget dropHandler = GetDropHandler((UIElement)sender);
if (dropHandler != null)
{
dropHandler.DragOver(dropInfo);
}
else
{
DefaultDropHandler.DragOver(dropInfo);
}
// Update the drag adorner.
if (dropInfo.Effects != DragDropEffects.None)
{
if (DragAdorner == null && _dragInfo != null)
{
CreateDragAdorner();
}
if (DragAdorner != null)
{
DragAdorner.MousePosition = e.GetPosition(DragAdorner.AdornedElement);
DragAdorner.InvalidateVisual();
}
}
else
{
DragAdorner = null;
}
// If the target is an ItemsControl then update the drop target adorner.
if (itemsControl != null)
{
// Display the adorner in the control's ItemsPresenter. If there is no
// ItemsPresenter provided by the style, try getting hold of a
// ScrollContentPresenter and using that.
UIElement adornedElement =
(UIElement)itemsControl.GetVisualDescendant <ItemsPresenter>() ??
(UIElement)itemsControl.GetVisualDescendant <ScrollContentPresenter>();
if (adornedElement != null)
{
if (dropInfo.DropTargetAdorner == null)
{
DropTargetAdorner = null;
}
else if (!dropInfo.DropTargetAdorner.IsInstanceOfType(DropTargetAdorner))
{
DropTargetAdorner = DropTargetAdorner.Create(dropInfo.DropTargetAdorner, adornedElement);
}
if (DropTargetAdorner != null)
{
DropTargetAdorner.DropInfo = dropInfo;
DropTargetAdorner.InvalidateVisual();
}
}
}
e.Effects = dropInfo.Effects;
e.Handled = true;
Scroll((DependencyObject)sender, e);
}