public ContentTypeViewModel() { Title = "DevDays Content Types"; ContentTypes = new ObservableRangeCollection <Document>(); LoadCommand = new Command(async() => await ExecuteLoadDocumentsCommand()); MessagingCenter.Subscribe <NewContentTypePage, Document>(this, "AddContentType", async(obj, contentType) => { var _contentType = contentType; if (_contentType == null) { return; } ContentTypes.Add(_contentType); await DataStore.AddContentTypeAsync(_contentType); }); }