I am afraid using the same approach on a MultiSelect widget with virtualization enabled would not be possible. The reason is the elements and the data items in the widget are virtualized. That means different items will use the same DOM element depending on the exact scroll position. On the other hand, there will be cases when not all intermediate items will be present in the widget DataSource. That will make their selection impossible.
As a side note, in case you have any further questions on a different widget, which was not part of the original question (e.g. the Grid), I would recommend you to open a separate thread for that. This way we will be able to keep each thread focused.
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