Generally the virtual collection was designed for ReadOnly purposes only and it is not recommended to be used in other scenarios.
As to selection with VirtualQueryableCollectionView, it is only supported when the selected items are in the View area. I am afraid it is not possible to select items outside it as the item to be eventually displayed is still not presented. This is the case until the user scrolls to a particular position so that the items to be displayed into view are actually loaded.
I would suggest you to use QueryableCollectionView and DataPager intead.
I hope this helps.
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