[MSCE U9 C++]为什么用mdlElement_setDisplayStyle函数设置元素的显示样式无效?

	IndexedViewportP viewPort = IViewManager::GetActiveViewSet().GetSelectedViewport();
	if (viewPort == nullptr)
	{
		return false;
	}
	DgnFileP dgnFile = viewPort->GetRootModel()->GetDgnFileP();
	DisplayStyleCP pDisStyle = DisplayStyleManager::FindDisplayStyleByName(L"Smooth", dgnFile);
	if (!pDisStyle)
	{
		return false;
	}
	int iIndex = pDisStyle->GetIndex();
	ElementId eleId = 968;
	MSElement ele;
	mdlAssoc_getElement(&ele, nullptr, eleId, ACTIVEMODEL);
	if (SUCCESS != mdlElement_setDisplayStyle(&ele, iIndex))
	{
		return false;
	}
	MSElementDescrP pEleDescr;
	mdlAssoc_getElementDescr(&pEleDescr, nullptr, eleId, ACTIVEMODEL, true);
	UInt32 posOld = elementRef_getFilePos(pEleDescr->h.elementRef);
	UInt32 posNew = mdlElmdscr_rewrite(pEleDescr, NULL, posOld);
	if (posOld != posNew)
	{
		return false;
	}
	return true;