// When Delete button is pressed
        private async void OnDeletePhoneCall() {
            var messageDialog = new MessageDialog("Delete this PhoneCall?", "Delete confirmation");
            messageDialog.Commands.Add(new UICommand("Cancel", (command) =>
            {
            }));

            messageDialog.Commands.Add(new UICommand("Delete", async (command) =>
            {
                try {
                    LoadingData = true;
                    CrudResult = await _phoneCallRepository.DeletePhoneCallAsync(SelectedPhoneCall.Id);
                    _eventAggregator.GetEvent<PhoneCallDeletedEvent>().Publish(SelectedPhoneCall);
                }
                catch (HttpRequestException ex) {
                    ErrorMessageTitle = ErrorMessagesHelper.DeletePhoneCallFailedError;
                    ErrorMessage = ex.Message;
                }
                finally {
                    LoadingData = false;
                    RunAllCanExecute();
                    _navService.GoBack();
                }
            }));

            messageDialog.DefaultCommandIndex = 0;
            await messageDialog.ShowAsync();

            if (ErrorMessage != null && ErrorMessage != string.Empty) {
                messageDialog = new MessageDialog(ErrorMessage, ErrorMessageTitle);
                await messageDialog.ShowAsync();
                _navService.GoBack();
            }
        }
        public async override void OnNavigatedTo(object navigationParameter, Windows.UI.Xaml.Navigation.NavigationMode navigationMode, Dictionary<string, object> viewModelState) {
            base.OnNavigatedTo(navigationParameter, navigationMode, viewModelState);

            // Note: Each time app selects from main page (PhoneCallListPage) detail page (PhoneCallDetailPage) is recreated.
            // Meaning that constructor is run and SelectedPhoneCall is null.
            // If SuspendAndTerminate (e.g. debug mode) SelectedPhoneCall is saved to SessionState (because of [RestorableState] attribute).
            // Therefore, if SelectedPhoneCall has been saved, use it instead of doing GetPhoneCallAsync.
            if (SelectedPhoneCall == null) {
                string errorMessage = string.Empty;
                int phoneCallId = (int)navigationParameter;

                if (phoneCallId == 0) {
                    SelectedPhoneCall = new PhoneCall();
                    SelectedPhoneCall.ValidateProperties();
                    RunAllCanExecute();
                }
                else {
                    try {
                        LoadingData = true;
                        CrudResult = await _phoneCallRepository.GetPhoneCallAsync(phoneCallId);
                        SelectedPhoneCall = JsonConvert.DeserializeObject<List<PhoneCall>>(CrudResult.Content.ToString()).FirstOrDefault<PhoneCall>();
                    }
                    catch (HttpRequestException ex) {
                        ErrorMessageTitle = ErrorMessagesHelper.HttpRequestExceptionError;
                        //TODO: Log stack trace to database here
                        ErrorMessage = string.Format("{0}", ex.Message);
                    }
                    finally {
                        LoadingData = false;
                    }
                    if (ErrorMessage != null && ErrorMessage != string.Empty) {
                        MessageDialog messageDialog = new MessageDialog(ErrorMessage, ErrorMessageTitle);
                        await messageDialog.ShowAsync();
                        _navService.GoBack();
                    }
                }
            }

            RunAllCanExecute();
        }
        // When Update button is pressed
        private async void OnUpdatePhoneCall() {
            string errorMessage = string.Empty;
            bool isCreating = false;

            SelectedPhoneCall.ValidateProperties();
            var updateErrors = SelectedPhoneCall.GetAllErrors().Values.SelectMany(pc => pc).ToList();

            if (updateErrors.Count == 0) {
                try {
                    LoadingData = true;
                    if (SelectedPhoneCall.Id == 0) {
                        isCreating = true;
                        CrudResult = await _phoneCallRepository.CreatePhoneCallAsync(SelectedPhoneCall);
                        SelectedPhoneCall = JsonConvert.DeserializeObject<List<PhoneCall>>(CrudResult.Content.ToString()).FirstOrDefault<PhoneCall>();
                    }
                    else {
                        CrudResult = await _phoneCallRepository.UpdatePhoneCallAsync(SelectedPhoneCall);
                    }
                }
                catch (ModelValidationException mvex) {
                    // there were server-side validation errors
                    DisplayPhoneCallErrorMessages(mvex.ValidationResult);
                }
                catch (HttpRequestException ex) {
                    ErrorMessageTitle = isCreating ? ErrorMessagesHelper.CreatePhoneCallFailedError : ErrorMessagesHelper.UpdatePhoneCallFailedError;
                    ErrorMessage = ex.Message;
                }
                finally {
                    LoadingData = false;
                    RunAllCanExecute();
                }

                if (ErrorMessage != null && ErrorMessage != string.Empty) {
                    MessageDialog messageDialog = new MessageDialog(ErrorMessage, ErrorMessageTitle);
                    await messageDialog.ShowAsync();
                    _navService.GoBack();
                }
            }
            else {
                RunAllCanExecute();
            }
        }