如何遍历参考文件中的所有可见element并把它们原位复制到当前模型中呢?

我目前能把参考文件参进来(这里是参考自身):

            DgnModel m = Session.Instance.GetActiveDgnModel();
            DgnDocumentMoniker moniker = m.GetDgnFile().GetDocument().GetMoniker();
            DgnAttachment attachment = m.CreateDgnAttachment(moniker, "模板(三角形)");
            
            attachment.SetLocateLock(true);
            attachment.SetSnapLock(true);
            ModelElementsCollection elements = attachment.GetDgnModel().GetGraphicElements();
            foreach (Element element in elements)
            {
                if (element.IsInvisible) continue;
                element.AddToModel();
                NotificationManager.OutputPrompt(cnt.ToString());
            }
            m.DeleteDgnAttachment(attachment);

但是复制element就不行(AddToModel)