Hi Kamlesh,
The Drag&Drop uses routed events which are quite powerful and allow you to handle events at object for which you do not have a direct reference.
You can use a class handler to add a handler for the DragQuery event for all TreeViewItems, so they will expand whenever someone wants to drop something in them.
Here is the code for adding the class event:
| static DragDropGridToTree() |
| { |
| EventManager.RegisterClassHandler(typeof(RadTreeViewItem), RadDragAndDropManager.DropQueryEvent, new EventHandler<DragDropQueryEventArgs>(OnTreeViewItemDropQuery)); |
| } |
| |
| private static void OnTreeViewItemDropQuery(object sender, DragDropQueryEventArgs e) |
| { |
| var treeViewItem = sender as RadTreeViewItem; |
| if (treeViewItem != null) |
| { |
| treeViewItem.IsExpanded = true; |
| } |
| } |
You first need to accept the drop operation, this happens by handling the DropQuery event. There the TreeView says "Yes, I accept the drop" and after the source is asked as well, (and user has not canceled the drag/drop) the tree view will receive notification for a successful drop.
I have attached the project from my previous post with the auto-expand and the Query events hooked. It is a more real-world example where the TreeView has different types as items (Organizations & People), everything is databound.
You can also have a look at the draft version for the DragDrop help which I have also included.
Greetings,
Miroslav
the Telerik team
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