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Changes between Initial Version and Version 6 of Ticket #2241

Ticket #2241
- Property Owner set to abeham
- Property Status changed from new to reviewing
- Property Summary changed from ItemsRemoved event uses Items instead of OldItems to store removed items to ItemsRemoved event handling is incorrect in some places

initial	v6
1		For most of our observable collections one has to subscribe to 4 events (ItemsAdded, ItemsReplaced, ItemsRemoved, and CollectionReset) to get notified of any change to the collection. Because of the reuse and generic design of the common event argument type it seems as if it was possible to handle these with one event handler. Unfortunately, ItemsRemoved is the exception in that it uses the `Items` property and not the `OldItems` property of the event argument to store the removed items.
	1	A couple of item collection event handlers were implemented incorrectly for ItemsRemoved events.
	2	Unification in event handling would be possible if ItemsRemoved was using OldItems property to store removed items. This is described in ticket: #2297.
2	3
3		It should be evaluated if the design could be improved, e.g. these events could be unified to one event and thus requiring only one subscription if the Items and OldItems property would be used consistently.
	4	Here the bugs should be fixed.