TreeView with derived TreeViewNodes crashes in WinUI3 Desktop

[eleanorleffler]

Describe the bug

TreeView using derived TreeViewNodes causes crash in WinUI3 Desktop. TreeView using derived TreeViewNodes works in UWP.

Steps to reproduce the bug

1. Checkout WinUI3 Problems TreeView repository.
2. Go to TreeViewWinUI folder.
3. Open the TreeViewWinUI solution.
4. Build and Run with Debug x64.
5. You should see that an exception was thrown. See Screenshot#1 for details.

Expected behavior

We expect the TreeView using inherited TreeViewNodes to behave as it does in UWP. We expect to see two TreeViews - one on the left and another on the right.

See Screenshot#2 for exact expected behavior.

Build and run TreeViewUWP solution inside the TreeViewUWP folder to see expected behavior.

Screenshots

Screenshot#1 - Current Behavior

Screenshot#2 - Expected Behavior

Version Info

NuGet package version:

[Microsoft.VCRTForwarders.140 1.0.6]
[Microsoft.WinUI 3.0.0-preview1.200515.3]

Targeting:
Target: Universal Windows
Target version: Windows 10, version 1809 (10.0; Build 17763)
Min version: Windows 10, version 1809 (10.0; Build 17763)

Windows 10 version	Saw the problem?
Insider Build (xxxxx)
November 2019 Update (18363)
May 2019 Update (18362)
October 2018 Update (17763)	Yes
April 2018 Update (17134)
Fall Creators Update (16299)
Creators Update (15063)

Device form factor	Saw the problem?
Desktop	Yes
Mobile
Xbox
Surface Hub
IoT

Additional context

Extra debugging

• If we collapse treeView1, the application still crashes.
  To replicate this, change the Visibility on line 34 in MainWindow.xaml to "Collapsed".
  Line 34: Visibility="Collapsed"/>

• However, if we collapse treeView2, the application runs, but does not display the TreeView with the inherited TreeViewNodes.
  To replicate this, change the Visibility on line 40 in MainWindow.xaml to "Collapsed".
  Line 40: Visibility="Collapsed"/>

[StephenLPeters]

@stevenbrix This sounds familiar, is there a CSWinrt issue that is preventing deriving from types?

[anawishnoff]

This bug has been fixed, and the fix will be available in our next release - WinUI 3 Preview 4. We're hoping to ship this preview release in early February. Thanks!