Not possible to select treeview nodes programmatically

[knightmeister]

Describe the bug
Previous Windows tree views had properties such as SelectedNodes which allowed you to set the nodes which are selected/highlighted in the control.

The UWP treeview exposes a SelectedNodes property which is a collection. The collection is read only and calling .Add on it and specifying a TreeViewNode does not add it to the collection and does not select the item in the user interface.

An IsSelected property should also be added to TreeViewNode to match with TreeViewItem.

Steps to reproduce the bug
Add items to a TreeView and then use the following code, which you would expect would select the first item.

if (treeView.RootNodes.Count > 0)
                treeView.SelectedNodes.Add(treeView.RootNodes[0]);

SelectedNodes = 0

Expected behavior
The first tree node would be selected.

Version Info
1809

[jevansaks]

@kaiguo Is this something you fixed recently or is it part of the pending PR you have out?

[kaiguo]

SelectedNoes collection only works in multi-select mode, @knightmeister can you set TreeView to multi-select and see if it still repros?

We are working on adding a new SelectedNode property for single selection, see PR #243.

[jevansaks]

Shouldn't we make SelectedNodes contain the one and only selected item in single select? I'm pretty sure Selector.SelectedItems works this way.

[kaiguo]

@jevansaks Yeah I think that works, then we can probably just get rid of the singular form SelectedItem and SelectedNode?

[knightmeister]

@kaiguo Yes, it works when SelectionMode=Multiple.

[jevansaks]

@jevansaks Jevan Saks FTE Yeah I think that works, then we can probably just get rid of the singular form SelectedItem and SelectedNode?

No, having the singular one is still convenient when in single select mode.

[kaiguo]

I see. I'll make some updates in #243

[jevansaks]

Ok, i'll assign this to you then.

[dpaulino]

Just wanted to chime in and ask if there's any progress on this? I really need to be able to programmatically set the selected item

[kaiguo]

Just wanted to chime in and ask if there's any progress on this? I really need to be able to programmatically set the selected item

Hey @dpaulino, sorry I've been working on rounded corners stuff. Will get back to this some time next week hopefully.

[msft-github-bot]

🎉This issue was addressed in #243, which has now been successfully released as Microsoft.UI.Xaml v2.2.190731001-prerelease.:tada:

Handy links:

• Release Notes
• Official Nuget Release

[dpaulino]

@kaiguo hey, just wanted to triple check. With your PR regarding this, should I now be use TwoWay binding for SelectedItem. Like this?

<u:WorkspaceTreeView 
    x:Name="Tree" 
    ItemsSource="{x:Bind ViewModel.WorkspaceItems, Mode=OneWay}"
    SelectedItem="{x:Bind ViewModel.SelectedItem, Mode=TwoWay}"

[kaiguo]

@kaiguo Kai Guo FTE hey, just wanted to triple check. With your PR regarding this, should I now be use TwoWay binding for SelectedItem.

Yes, you can use binding like that for single selection.
SelectedItems for multi-select is still read only (we kept it consistent with ListView), so you'll have to do it through a TreeView instance, like the example we showed in this spec.

[dpaulino]

Okay thanks for confirming. I think I'm getting an access violation error when I use two way binding though... But I'll try to get a proper repro, and I'll create a new issue if I see any issues