private void Choose(object obj) { if (!string.IsNullOrEmpty(_selectedFile)) { switch (_cloudService) { case CloudServiceType.Dropbox: _logger.Info("get dropbox access from database"); var dropboxAccess = _database.GetSingleByName <DropboxAccess>(DropboxAccess.ObjectName); if (dropboxAccess != null) { _logger.Info("download file from dropbox"); _dropboxService.DownloadFile(dropboxAccess.AccessToken, _selectedFile); _messenger.Send(new FileListCancelMsg()); } break; default: throw new ArgumentOutOfRangeException(); } } else { _messenger.Send(new SelectedFileIsNullOrEmptyMsg()); } }