You can achieve the described requirements by creating custom boolean attached property. Once you create it you will be able to bind it to a property from your ViewModel. This will allow you to trigger it from your ViewModel. On the other hand, in the PropertyChanged callback of the attached property you will be able to clear the CheckedItems collection using the DependencyObject argument.
In addition to this the RadDataBoundListBox control exposes ItemCheckedStateChanged event. You can subscribe to it and you will be able to set back the property of your view model to its initial state when the event is invoked.
I believe this will get you started. Do not hesitate to contact us again if you need any further assistance.
Pavel R. Pavlov
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