private void GalleryTap()
 {
     if (PHPhotoLibrary.AuthorizationStatus == PHAuthorizationStatus.Authorized)
     {
         var descriptionViewController = new PhotoPreviewViewController();
         NavigationController.PushViewController(descriptionViewController, true);
     }
     else
     {
         UIApplication.SharedApplication.OpenUrl(new NSUrl(UIApplication.OpenSettingsUrlString), new NSDictionary(), null);
     }
 }
        private void GoToDescription(UIImage image, UIDeviceOrientation orientation, NSDictionary metadata = null)
        {
            var descriptionViewController = new PhotoPreviewViewController(image, orientation, metadata);

            NavigationController.PushViewController(descriptionViewController, true);
        }