If you’ve ever used an AdvancedDataGrid, chances are you’ve encountered HierarchicalCollectionView. If you’ve ever used an AdvancedDataGrid for anything remotely complex, chances are you’ve cursed and shaken your metaphorical fists at HierarchicalCollectionView.

There are likely myriad reasons to despise this class but the one that burned me was this gem: any filterFunction applied to your HierarchicalCollectionView is also applied directly to your underlying child collections. In case the ramifications of that are not immediately clear, what it means is that you cannot simultaneously have two distinct views of a single data set that you have wrapped into a HierarchicalCollectionView. In fact, once applied you will have to manually clear the filter from underlying collections in order to get them back to normal. Because of this, the class is of extremely limited utility, and I would submit that its name is highly misleading. The ‘View’ at the end of the name implies that it will be creating a “virtual” view of the underlying data, leaving the source intact. This is how the immensely useful ListCollectionView class works. Apparently, other languages/frameworks also have “collection view” classes that do not modify the underlying data, so this is quite a departure from convention, not to mention common sense.

If you happen to look at the docs for HierarchicalCollectionView you will notice that filterFunction isn’t even listed as a supported property. Maybe the thinking was if they don’t tell anyone about it, we’ll overlook how poorly implemented it is?