ArcEngine怎样符号化cad annotation图层？

参考下面代码：
 //打开CAD数据集
            IWorkspaceFactory pWorkspaceFactory = new CadWorkspaceFactoryClass();
            IFeatureWorkspace pFeatureWorkspace = (IFeatureWorkspace)pWorkspaceFactory.OpenFromFile(@"D:\E_new\ZhuXinying\testData\CAD数据", 0);
            //打开一个要素集
            IFeatureDataset pFeatureDataset = pFeatureWorkspace.OpenFeatureDataset("地形图--a区.dwg");
            //IFeaturClassContainer可以管理IFeatureDataset中的每个要素类
            IFeatureClassContainer pFeatureClassContainer = (IFeatureClassContainer)pFeatureDataset;
            //对CAD文件中的要素进行遍历处理
            for (int i = 0; i < pFeatureClassContainer.ClassCount; i++)
            {
                IFeatureClass pFeatureClass = pFeatureClassContainer.get_Class(i);
                if (pFeatureClass.FeatureType == esriFeatureType.esriFTCoverageAnnotation)//注意：不是esriFeatureType.esriFTAnnotation
                {

                    IFeatureLayer pFeatureLayer = new CadAnnotationLayerClass();
                    pFeatureLayer.FeatureClass = pFeatureClass;
                    pFeatureLayer.DataSourceType = "CAD Annotation Feature Class";
                    ((ILayer)pFeatureLayer).Name = "anno";
                    axMapControl1.AddLayer(pFeatureLayer as ILayer);

                    axMapControl1.Refresh();
                }
            }

请教一下，mdb里的esriFeatureType.esriFTAnnotation类型要素图层，怎么加载?c# ae开发.