private WebDavNavigationService()
 {
     _navigationService = BootStrapper.Current.NavigationService;
     _navigationService.FrameFacade.BackRequested    += OnBackRequested;
     _navigationService.FrameFacade.ForwardRequested += OnForwardRequested;
     _itemService = WebDavItemService.GetDefault();
     BackStack    = new ObservableCollection <DavItem>();
     ForwardStack = new ObservableCollection <DavItem>();
     Items        = new ObservableCollection <DavItem>();
 }
 public static WebDavItemService GetDefault()
 {
     return(_instance ?? (_instance = new WebDavItemService()));
 }