public MainWindowViewModel()
        {
            _elementsRibbonGroupViewModel = new ElementsRibbonGroupViewModel(_document, _documentState);
            _formattingRibbonGroupViewModel = new FormattingRibbonGroupViewModel(_document, _documentState);
            _stylesGroupViewModel = new StylesGroupViewModel(_document, _documentState);

            Messenger.Default.Register<byte[]>(this, "down", OnOpenDropboxFileMessage);
            Messenger.Default.Register<Object>(this, "req", OnSaveDropboxFileMessage);
        }
        public MainWindowViewModel()
        {
            _elementsRibbonGroupViewModel   = new ElementsRibbonGroupViewModel(_document, _documentState);
            _formattingRibbonGroupViewModel = new FormattingRibbonGroupViewModel(_document, _documentState);
            _stylesGroupViewModel           = new StylesGroupViewModel(_document, _documentState);

            Messenger.Default.Register <byte[]>(this, "down", OnOpenDropboxFileMessage);
            Messenger.Default.Register <Object>(this, "req", OnSaveDropboxFileMessage);
        }