ArcEngine 图层通过DisplayAnnotation设置标注后无法释放数据库占用（不设置DisplayAnnotation可以正常释放），请问需要怎么设置才能释放掉数据库的占用？

private void Form1_Load(object sender, EventArgs e)
{
            IWorkspaceFactory wf = new AccessWorkspaceFactory();
            IFeatureWorkspace fws = wf.OpenFromFile(@"C:\Users\ASUS\Desktop\1\不动产数据库成果.mdb", 0) as IFeatureWorkspace;
            IFeatureClass f = fws.OpenFeatureClass("ZDJBXX");
            IFeatureLayer featLyr = new FeatureLayer();
            featLyr.FeatureClass = f;
            axMapControl1.AddLayer(featLyr as ILayer);
            IGeoFeatureLayer geoLyr = featLyr as IGeoFeatureLayer;
            geoLyr.DisplayAnnotation = true;

            Marshal.FinalReleaseComObject(fws);
            Marshal.FinalReleaseComObject(f);
            Marshal.FinalReleaseComObject(featLyr);
}