Hi Thank you for your reply. I am afraid I don't quite understand your answer. What is a ServiceClient? I think you didn't understand my question. This is on the server(service) side, of the distributed app. not on the client, so there is no ServiceClient! I am trying to execute the callback method, using the async pattern. The call to the callback method is placed in the try-catch block because in case the client is not present any more, the call to that method throws an exception, so placing the call to the finnaly block would crash the program. Uros