protected ICollection <Guid> GetMetadataExtractorIdsForMediaCategories(IEnumerable <string> mediaCategories) { IMediaAccessor mediaAccessor = ServiceRegistration.Get <IMediaAccessor>(); ICollection <Guid> result = new HashSet <Guid>(); foreach (string mediaCategory in mediaCategories) { CollectionUtils.AddAll(result, mediaAccessor.GetMetadataExtractorsForCategory(mediaCategory)); } return(result); }