There are no attachments in the forum thread, but that's OK. The reason you do not get any IDs passed to the server is because RadTreeView nodes do not have IDs of their own. When listview items are dropped on HTML elements, the client ID of the destination element is passed to the server. If the latter does not have an IDs, you do not get anything.
To work around this, there are a couple of options you can take:
Option 1. Give an id to your destination element dynamically. You can use RadListView's client-side OnItemDropping event to get the destination element and give it an id:
el = args.get_destinationElement();
(el && !el.id)
Of course, you can use Templates for RadTreeView and put an element with an ID where the listview item would be dropped. That's just one option
Option 2. Use some other means to save custom data that will be useful on the server. For example, you can save the inner HTML of the target tree view node into a hidden field on page. Then you can use this value in the ItemDrop server event event of the list view instead of the destination HTML id.
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