Expander crashes the app when nested with an ItemsRepeater

[StanlsSlav]

Describe the bug

Having an ItemsRepeater in a Expander will crash the app. Other controls seem to work normally with the expander

<controls:Expander>
    <ItemsRepeater />
</controls:Expander>

Regression

No response

Reproducible in sample app?

• This bug can be reproduced in the sample app.

Steps to reproduce

1. Create a WinUI3 project using template *Blank App, Packaged (WinUI 3 in Desktop)* or the *Template Studio for WinUI*
2. Add the snippet from the bug description
2.1 Make sure the *controls* alias is set to *CommunityToolkit.WinUI.UI.Controls*
3. Run the app
4. Expand the Expanders

Expected behavior

The app will continue running and show the items from ItemsRepeater as with a normal one would.

Screenshots

No response

Windows Build Number

• Windows 10 1809 (Build 17763)
• Windows 10 1903 (Build 18362)
• Windows 10 1909 (Build 18363)
• Windows 10 2004 (Build 19041)
• Windows 10 20H2 (Build 19042)
• Windows 10 21H1 (Build 19043)
• Windows 11 21H2 (Build 22000)
• Other (specify)

Other Windows Build number

No response

App minimum and target SDK version

• Windows 10, version 1809 (Build 17763)
• Windows 10, version 1903 (Build 18362)
• Windows 10, version 1909 (Build 18363)
• Windows 10, version 2004 (Build 19041)
• Other (specify)

Other SDK version

No response

Visual Studio Version

2022

Visual Studio Build Number

17.3.2

Device form factor

Desktop

Nuget packages

	Version
CommunityToolkit.WinUI.UI	7.1.2
CommunityToolkit.WinUI.UI.Controls	7.1.2
Microsoft.WindowsAppSDK	1.1.4
Microsoft.Windows.SDK.BuildTools	10.0.22621.1

Additional context

No response

Help us help you

No.

[ghost]

Hello StanlsSlav, thank you for opening an issue with us!

I have automatically added a "needs triage" label to help get things started. Our team will analyze and investigate the issue, and escalate it to the relevant team if possible. Other community members may also look into the issue and provide feedback 🙌

[Arlodotexe]

Was able create a minimal repro of the issue using the steps provided: App1.zip

We'll look into fixing this as part of the 7.1.3 or 7.2 release.

[michael-hawker]

@StanlsSlav do you need the Expander in Left/Right mode? Otherwise, you should just use the built-in WinUI expander instead.

@Arlodotexe we plan to try and rebuild on top of the WinUI Expander for 8.0; so I don't think we should fix this unless it's something super trivial.

[StanlsSlav]

In left mode.

[michael-hawker]

Will investigate as part of the work we want to do in https://aka.ms/toolkit/labs/windows for building Expander on top of the system Expander.

[TimoB90]

Hello will there be a fix for this?

I have the same issue with SettingsExpander if I use "ItemsControl" or "ItemsRepeater". Strange is, that everything works fine, if I test it in visual studio. But as soon as I start it via the packed app .exe and open the expander. Everything crashes

[michael-hawker]

@TimoB90 SettingsExpander uses the platform Expander, not this original toolkit one, so that sounds like a different issue.

If you turn on native debugging and first-chance exceptions you may be able to get more details about what is happening. If a crash is coming from inside Expander, you'd want to file an issue with the platform.