Treeview how do I tell when the user reorganizes the treeview by dragging nodes

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I have a TreeView that the user can edit. I need to know whenever it changes so that I can persist it. I do the additions and deletions, so that is no problem. But the user can also restructure the tree by dragging and dropping the nodes. I haven't been able to determine what event(s) to listen for to tell when that is happening.

What I have tried:

I've tried the Drag and Drop events, but they were uncalled. I suppose the TreeView eats them itself. I've considered subclassing TreeViewNode and overriding all the Children IList members that could be used in that case, but was sure there must be a more civilised way.

Posted 26-Jun-18 10:57am

Member 13022351

Updated 30-Jun-18 22:30pm

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2 solutions

Solution 1

Maybe drag & drop is not supported for a UWP TreeView?

Drag and drop between treeview in uwp - Stack Overflow[^]

Posted 26-Jun-18 21:23pm

Dirk Bahle

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Member 13022351 27-Jun-18 3:38am

The UWP TreeView allows the user to move TreeViewNodes around the tree structure via drag and drop. It reorganizes the tree structure accordingly. For example, the user can drag a TreeViewNode from one parent to another parent thus altering the tree structure. My question is: how can I tell when this has happened? I haven't been able to find any events on TreeView that fire when this takes place.

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Member 13022351 · Accepted Answer · 2018-06-30T21:19:00

While the TreeView itself does not expose any events that indicate that the user has changed the structure of the tree, the TreeView control wraps a TreeViewList control. That control does expose drag events, like DragItemStarting. So the solution is to do this:

<Style TargetType="TreeView">
            <Setter Property="IsTabStop" Value="False" />
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="TreeView">
                        <TreeViewList x:Name="ListControl"
                                      DragItemsCompleted="DragItemsCompleted"
                                      CanDragItems="True"
                                      AllowDrop="True"
                                      CanReorderItems="True">

Thanks to Sunteen Wu from Microsoft for the answer!