public void BrowseForFile(EventHandler <BrowseCompleteEventArgs> onComplete, string[] fileExts = null, string startupFolderRelativePath = null, object userState = null)
        {
            if (_appServices == null)
            {
                throw new Exception("Application Services are unavailable.");
            }

            _appServices.BrowseForFile(onComplete, fileExts, startupFolderRelativePath, userState);
        }