Last Updated: 08 Apr 2020 06:59 by ADMIN
Created on: 06 Mar 2020 08:07
Category: TreeView
Type: Bug Report
Drag&Drop Payload Manager Data object is missing tree nodes when RadTreeView is virtualized


I found a bug when drag&dropping selected tree nodes (extended multi-selection) when the tree is virtualized. Items that never got into view are missing from the Payload Manager Data object. If virtualization is off, works as expected.

Please see modified sample for demonstration. I added 200+ items to League A -> Division A. Select the first item, quickly scroll by dragging vertical scrollbar to the bottom of the list and extend selection to the whole list. Then perform drag and drop. Note, not all items were moved.

Also, the drag visual helper moves and updates very very slowly when dragging hundredths of objects. In our application, we have thousands of objects, which makes it unusable


Thank you for a quick fix.


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1 comment
Martin Ivanov
Posted on: 12 Mar 2020 16:22

Hello Tomas,

This happens because the built-in drag/drop functionality works with the item containers (RadTreeViewItem elements). When the containers are not in the viewport, they are not realized, therefore a snapshot cannot be taken. This is a limitation of the drag/drop feature and we have a feature request to improve it in this scenario. 

Currently, the way to go would be to disable the default drag/drop and implement a custom one from scratch using the DragDropManager. This will allow you to work with the models in the ItemsSource and manually move them around the collections in the hierarchy. You can find several SDK examples that show drag/drop customization that could be a good starting point.

Martin Ivanov
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