TreeView Page - SelectionMode = Multiple Causes Win Error

[keithnicholson]

Describe the bug

If you generate a new template and add the TreeView page, then change the SelectionMode of the control to Multiple, it eventually causes an error.

To Reproduce

1. Go to an new or existing Template Studio Template.
2. If new, add a TreeView Page, if existing, use the Context Menu to add a new TreeView Page.
3. Open the view for the page to see XAML.
4. Change the SelectionMode from 'Single' to 'Multiple'
5. Build the application
6. Navigate to the new page
7. See the Checkbox/Multi-Select box
8. Click on any box, top level or bottom level
9. See error:

Additional context

Here is a link to a repo for you to try:

TreeViewOnly Repo

Here is a log from Event Viewer:

Applies to the following platforms:

• [ ] WinUI
• [ ] WPF
• [X] UWP

About your setup

• Visual Studio Version: VS2019
• Template Studio Wizard Version: 4.1.21179.1
• Windows Build: Version 10.0.22000 Build 22000 (However, I can replicate the exact issue on a number of Win 10 builds.)