PhotosGetNotInSet() public method

Gets a list of photos not in sets. Defaults to include all extra fields.
public PhotosGetNotInSet ( ) : Photos
return Photos
        public IEnumerable <DiscoveredFile> Discover(string path, HashSet <string> existingSources)
        {
            string photosetId = path.Replace("/", "");
            int    page       = 1;
            int    maxPages   = 1;

            while (page <= maxPages)
            {
                // existing sources gives us a list of photoset ids
                PagedPhotoCollection photos;
                try
                {
                    if (photosetId == "")
                    {
                        photos = _flickr.PhotosGetNotInSet(page, 100, PhotoSearchExtras.OriginalUrl | PhotoSearchExtras.Media | PhotoSearchExtras.LargeUrl);
                    }
                    else
                    {
                        photos = _flickr.PhotosetsGetPhotos(photosetId, PhotoSearchExtras.OriginalUrl | PhotoSearchExtras.Media | PhotoSearchExtras.LargeUrl, page, 100);
                    }
                    maxPages = photos.Pages;
                    page++;
                }
                catch
                {
                    photos = new PhotoCollection();
                }

                foreach (var photo in photos)
                {
                    if (!existingSources.Contains(path + photo.PhotoId))
                    {
                        if (photo.MediaStatus == "failed")
                        {
                            continue;
                        }
                        string url = photo.OriginalUrl;
                        if (url == null)
                        {
                            url = photo.LargeUrl;
                        }
                        if (url == null)
                        {
                            url = photo.MediumUrl;
                        }
                        string extension = System.IO.Path.GetExtension(url);
                        if (photo.Media == "video")
                        {
                            url = $"http://www.flickr.com/video_download.gne?id={photo.PhotoId}";

                            try
                            {
                                if (!photo.IsPublic)
                                {
                                    _flickr.PhotosSetPerms(photo.PhotoId, true, photo.IsFriend, photo.IsFamily, PermissionComment.Nobody, PermissionAddMeta.Owner);
                                }
                                string fileName = GetHeaderFileName(url);
                                extension = System.IO.Path.GetExtension(fileName);
                                if (!photo.IsPublic)
                                {
                                    _flickr.PhotosSetPerms(photo.PhotoId, photo.IsPublic, photo.IsFriend, photo.IsFamily, PermissionComment.Nobody, PermissionAddMeta.Owner);
                                }
                            }
                            catch (Exception ex)
                            {
                            }
                        }

                        yield return
                            (new DiscoveredFile
                        {
                            Name = photo.Title,
                            Path = path + photo.PhotoId,
                            Extension = extension,
                            Url = url
                        });
                    }
                }
            }
        }