Yesterday, I was trying to write a custom hierarchical cursor class that implements the IHierarchicalCollectionViewCursor interface. But no matter what I tried, the AdvancedDataGrid would not recognise my implemented cursor class as being hierarchical. When I extended the existing HierarchicalCollectionViewCursor class, the AdvancedDataGrid would happily recognise it - even I overrode every single method and property... yet, as soon as I switched the class to implement IHierarchicalCollectionViewCursor instead of extending HierarchicalCollectionViewCursor, the AdvancedDataGrid would break again.

At work, we've been having some significant performance issues with the Flex AdvancedDataGrid control, so my boss has begun a dialog with some of the AdvancedDataGrid control's developers over at Adobe. As part of that dialog, my boss asked me to write a brief summary of the problem - which I've done. But it has occurred to me that the problem description is likely to be very interesting to some people, so I've decided to publish it here too. And so, here it is...