private void SwitchToViewState(FeedbackViewState newViewState, bool isBackOperation = false)
        {
            Deployment.Current.Dispatcher.BeginInvoke(() =>
            {
                switch (newViewState)
                {
                case FeedbackViewState.MessageForm:
                    ShowFormAppBar();
                    this.FeedbackPageContent.Content = formControl;
                    break;

                case FeedbackViewState.MessageList:
                    ShowListAppBar();
                    this.FeedbackPageContent.Content = listControl;
                    break;

                case FeedbackViewState.ImageEdit:
                    imageControl.VM = this.VM.CurrentImageVM;
                    ShowDrawAppBar();
                    this.FeedbackPageContent.Content = imageControl;
                    break;

                case FeedbackViewState.ImageShow:
                    imageControl.VM = this.VM.CurrentImageVM;
                    ShowDrawAppBar();
                    this.FeedbackPageContent.Content = imageControl;
                    break;

                case FeedbackViewState.Unknown:
                    NavigationService.GoBack();
                    break;

                default:
                    break;
                }
                if (!isBackOperation)
                {
                    lastActiveViewStates.Add(CurrentViewState);
                }
                CurrentViewState = newViewState;
            });
        }
 private void SwitchToViewState(FeedbackViewState newViewState, bool isBackOperation = false)
 {
     Deployment.Current.Dispatcher.BeginInvoke(() =>
     {
         switch (newViewState)
         {
             case FeedbackViewState.MessageForm:
                 ShowFormAppBar();
                 this.FeedbackPageContent.Content = formControl;
                 break;
             case FeedbackViewState.MessageList:
                 ShowListAppBar();
                 this.FeedbackPageContent.Content = listControl;
                 break;
             case FeedbackViewState.ImageEdit:
                 imageControl.VM = this.VM.CurrentImageVM;
                 ShowDrawAppBar();
                 this.FeedbackPageContent.Content = imageControl;
                 break;
             case FeedbackViewState.ImageShow:
                 imageControl.VM = this.VM.CurrentImageVM;
                 ShowDrawAppBar();
                 this.FeedbackPageContent.Content = imageControl;
                 break;
             case FeedbackViewState.Unknown:
                 NavigationService.GoBack();
                 break;
             default:
                 break;
         }
         if (!isBackOperation)
         {
             lastActiveViewStates.Add(CurrentViewState);
         }
         CurrentViewState = newViewState;
     });
 }