服务器返回数据问题

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//取得服务端返回的结果
MSXML2::IXMLDOMDocument *pXMLDoc;
MSXML2::IXMLDOMNode *pXDN;

IDispatch *ppBody;
hr = pIXMLHTTPRequest->get_responseXML(&ppBody);
SUCCEEDED(hr) ? S_OK : throw hr;

hr = CoInitialize(NULL);
SUCCEEDED(hr) ? S_OK : throw hr;
hr = CoCreateInstance(CLSID_DOMDocument, NULL, CLSCTX_INPROC_SERVER, IID_IXMLDOMDocument, (void**)&pXMLDoc);
SUCCEEDED(hr) ? S_OK : throw hr;
系统提示CLSID_DOMDocument，IID_IXMLDOMDocument都是未知字符串，为什么？

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自己顶上去