DocumentViewer TryGetDocumentViewer()
 {
     if (__documentViewer == null)
     {
         __documentViewer = DocumentViewer.TryGetInstance(wpfTextView);
     }
     return(__documentViewer);
 }
 DocumentViewer TryGetInstance() =>
 __documentViewer ?? (__documentViewer = DocumentViewer.TryGetInstance(textView));