private void _ScanDirectories(object obj)
        {
            if (m_directoryMonitor == null)
            {
                return;
            }

            if (obj is IList <object> )
            {
                var selectedItems = obj as IList <object>;
                if (selectedItems == null)
                {
                    return;
                }

                for (int i = selectedItems.Count - 1; i >= 0; i--)
                {
                    if (selectedItems[i] is Filer.DirectoryMonitor.Directory)
                    {
                        Filer.DirectoryMonitor.Directory directory = selectedItems[i] as Filer.DirectoryMonitor.Directory;
                        if (directory == null)
                        {
                            return;
                        }

                        m_directoryMonitor.ScanDirectory(directory);
                    }
                }
            }
        }