async partial void ContentButtonClick(NSObject sender)
        {
            currentViewMode        = ContentMode.CM_Contents;
            ContentButton.State    = NSCellStateValue.On;
            IndexButton.State      = NSCellStateValue.Off;
            AnnotationButton.State = NSCellStateValue.Off;

            await HidePreNextButton(false);

            PageViewController.SetPageContentEmpty(true);
            PageViewController.SetIndexBannerLetter(null, false);
            BookContentView.Hidden = false;

            if (TOCDataManager.CurrentLeafNode != null)
            {
                PageViewController.AddLoadView();
                if (!this.IsInitialize)
                {
                    this.IsEnableAddNavigation = true;
                }
                await OpenPublicationContentAtTOCNode(BookID, TOCDataManager.CurrentLeafNode);
            }

            SetSideBarViewShowByMode();

            SetButtonAttributedTitle(ContentButton, LNRConstants.TITLE_CONTENT, true);
            SetButtonAttributedTitle(IndexButton, LNRConstants.TITLE_INDEX, false);
            SetButtonAttributedTitle(AnnotationButton, LNRConstants.TITLE_ANNOTATIONS, false);
        }
        private void SwitchToContentView()
        {
            currentViewMode        = ContentMode.CM_Contents;
            ContentButton.State    = NSCellStateValue.On;
            IndexButton.State      = NSCellStateValue.Off;
            AnnotationButton.State = NSCellStateValue.Off;

            HidePreNextButton(false);

            PageViewController.SetPageContentEmpty(true);
            PageViewController.SetIndexBannerLetter(null, false);
            BookContentView.Hidden = false;

            SetSideBarViewShowByMode();

            SetButtonAttributedTitle(ContentButton, LNRConstants.TITLE_CONTENT, true);
            SetButtonAttributedTitle(IndexButton, LNRConstants.TITLE_INDEX, false);
            SetButtonAttributedTitle(AnnotationButton, LNRConstants.TITLE_ANNOTATIONS, false);
        }