A small .NET 8 sample app that demonstrates an ItemStackPanel bug: when using a custom implementation of ICollectionView and ICollectionView.CollectionGroups, after items in a group are cleared, the panel does not properly clear/recycle item containers.

This project exists only to reproduce the issue microsoft/microsoft-ui-xaml#11085.

The custom implementation code for ICollectionView used in this repro is under the CustomImplementation folder.

1. Open GroupingTest.sln (or the project) in Visual Studio.
2. Build and run the app.
3. Click a single button on the UI to clear group items for each group.
4. Observe that the ItemsStackPanel does not clear containers from the UI.