With the current implementation of RadListBox
the desired by you functionality is not supported out of the box.
However, as you have already found you could easily achieve it using the MouseUp event of RadListBoxItem - attached you could find a sample project that demonstrates how to achieve it.
However, you could also log this as feature request in our Feedback Porta
l. We will review the item and will consider it for implementation.
Hope this helps.
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Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Feedback Portal
and vote to affect the priority of the items