public static void AddAnnotationReference(SceneElement element, AnnotationSceneNode annotation) { ExceptionChecks.CheckNullArgument <SceneElement>(element, "element"); ExceptionChecks.CheckNullArgument <AnnotationSceneNode>(annotation, "annotation"); string str = annotation.Id; if (string.IsNullOrEmpty(str)) { str = AnnotationUtils.SetAnnotationId(annotation); } IEnumerable <string> referencedAnnotationIds = AnnotationUtils.GetReferencedAnnotationIds(element); AnnotationUtils.SetAnnotationReferences(element, EnumerableExtensions.AppendItem <string>(referencedAnnotationIds, str)); }