private void treeView_PreviewMouseMove(object sender, MouseEventArgs e)
{
var item = (Item)treeView.SelectedItem;
if (item != null && item is InstanceItem && item != NoneItem && e.LeftButton == MouseButtonState.Pressed)
{
Vector offset = e.GetPosition(null) - dragStart;
// Start drag if mouse was held for a minimum distance
if (Math.Abs(offset.X) > SystemParameters.MinimumHorizontalDragDistance ||
Math.Abs(offset.Y) > SystemParameters.MinimumVerticalDragDistance)
{
// Allow dropping anywhere within the window
Window mainWindow = Application.Current.MainWindow;
mainWindow.AllowDrop = true;
// Create item ghost
var template = new DataTemplate(typeof(InstanceItem));
var textBlock = new FrameworkElementFactory(typeof(TextBlock));
textBlock.SetBinding(TextBlock.TextProperty, new Binding("DisplayName"));
template.VisualTree = textBlock;
var adornedElement = (UIElement)mainWindow.Content;
var adornerLayer = AdornerLayer.GetAdornerLayer(adornedElement);
dragAdorner = new DragAdorner(item, template, adornedElement, adornerLayer);
mainWindow.PreviewDragOver += MainWindow_PreviewDragOver;
// Perform drag and drop
DataObject data = new DataObject(typeof(InstanceItem), item);
DragDrop.DoDragDrop(treeView, data, DragDropEffects.Move);
// Cleanup handlers
mainWindow.PreviewDragOver -= MainWindow_PreviewDragOver;
dragAdorner.Detach();
mainWindow.AllowDrop = false;
}
}
}
