arcengine 如何得到注记图层属性中的annotation classes

IAnnotationLayerFactory pAnnotationFactory = new FDOGraphicsLayerFactoryClass() as IAnnotationLayerFactory;
IAnnotationLayer pAnnotationLayer= pAnnotationFactory .OpenAnnotationLayer(pFeatureWorkspace,pFeatureDataset,"hydlanno");
IFeaturelayer mFeatureLayer=pAnnotationLayer as IFeaturelayer ;
IFeaturelayer pFeatureLayer=mFeatureLayer.FeatureClass;
 
IGeoFeatureLayer pGeoFeaLayer=(IGeoFeatureLayer )pFeatureLayer;
//此处的注记属性集合的个数总是1，而且其class值总是“default”，而真实情况是这个注记层属性中有多个annotation classes，求哥哥姐姐指点
IAnnotateLayerPropertiesCollection pAnnoPropColl=pGeoFeaLayer.AnnotationProperties;