public MyEventViewModel(IDataService dataService) { _dataService = dataService; if (IsInDesignMode) { SelectedEvent = _dataService.GetEvents(1).FirstOrDefault(); Participants = new ObservableCollection<Participant>(_dataService.GetParticipant(1)); } Messenger.Default.Register<Event>(this, "SelectedEvent", evt => { if (evt != null) { LoadMyEvent(evt); } }); }