public PhotoViewModel(INavigationService navigationService)
        {
            Messenger.Default.Register<int>(this,
             picture =>
             {
             DataServicePicture dsPicture = new DataServicePicture();
             this.Trip = dsPicture.getPictureById(picture).Trip;
             SelectedPictureIndex = Trip.Pictures.OrderBy(x => x.Date).ToList().FindIndex(x => x.Id == picture);
             });

            this._navigationService = navigationService;
        }
 private Picture GetPictureInDB(int pictureId)
 {
     DataServicePicture dsPicture = new DataServicePicture();
     return dsPicture.getPictureById(pictureId);
 }