I suppose that your RadComboBox is read-only and in this case there will be always a selected item in it.
However you can add a “default” empty item to be displayed in the RadComboBox input.
In this way you will be able to "deselect" the initially selected item – you can find more details about this approach here.
If the issue persists, could you please explain your implementation in more details and send us a sample code? Thank you in advance.
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