public DirectoryStructureViewModel()
        {
            var children = DirectoryStructure.GetLogicalDrives();

            this.Items = new ObservableCollection <DirectoryItemViewModel>(
                children.Select(drive => new DirectoryItemViewModel(drive.FullPath, DirectoryItemType.Drive)));
        }
        private void Expand()
        {
            if (this.Type == DirectoryItemType.File)
            {
                return;
            }

            this.Children = new ObservableCollection <DirectoryItemViewModel>(DirectoryStructure.GetDirectoryContents(this.FullPath).Select(content => new DirectoryItemViewModel(content.FullPath, content.Type)));
        }