public SessionViewModel(int sessionId)
        {
            _conferenceService = new ConferenceService();
            _id = sessionId;

            var session = _conferenceService.LoadSession(_id);

            _speaker = session.Speaker;
            _title   = session.Title;
        }
        public SessionViewModel()
        {
            _conferenceService = new ConferenceService();

            //
            // XAML Patterns (4.5):
            //
            // When the SessionSelected message is received, load the session.
            //
            MessengerInstance.Register <SessionSelected>(this, message =>
            {
                var session = _conferenceService.LoadSession(message.SessionId);
                _id         = message.SessionId;
                Speaker     = session.Speaker;
                Title       = session.Title;
            });
        }