If you would like to stick to the void method then yes, the only way of notifying the silverlight application would be by throwing an exception. You can also modify the method to return some sort of a flag that will notify you if the operation has passed or not (be it boolean or something else that makes sense for you)
the Telerik team
Q1’11 SP1 of Telerik OpenAccess is available for download
; also available is the Q2'11 Roadmap
for Telerik OpenAccess ORM.