I am not quite sure that I understood your scenario. Assuming that you have 2 RadListBoxes populated with identical data and you want to disable the item from the second RadListBox, corresponding to the one, checked in the first RadListBox I could suggest you the following implementation :
sender, RadListBoxItemEventArgs e)
RadListBoxItem currentlyCheckedItem = e.Item;
(item2.Value == currentlyCheckedItem.Value)
item2.Enabled = item2.Enabled ?
is a video, demonstrating the behavior at my end.
the Telerik team
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