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Editorial Team
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Asked: 2026-06-15T08:53:11+00:00

I’m trying to output a formatted XML document from a DOM object into a

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I’m trying to output a formatted XML document from a DOM object into a string, as shown in the code below. The thing is, while the dom->get_xml() method does return a value, the MXXMLWriter->output does not, as you can see on the screenshot. All method calls return S_OK. What could be the issue here?

Here’s my code:

CComPtr<IMXWriter> w;
HRESULT hr;
hr = w.CoCreateInstance(__uuidof(MXXMLWriter), NULL, CLSCTX_INPROC_SERVER);

hr = w->put_indent(VARIANT_TRUE);

CComPtr<ISAXXMLReader> rd;
hr = rd.CoCreateInstance(__uuidof(SAXXMLReader60), NULL, CLSCTX_INPROC_SERVER);

CComPtr<ISAXContentHandler> hc;
hr = w.QueryInterface<ISAXContentHandler>(&hc);
CComPtr<ISAXErrorHandler> he;
hr = w.QueryInterface<ISAXErrorHandler>(&he);
CComPtr<ISAXDTDHandler> hd;
hr = w.QueryInterface<ISAXDTDHandler>(&hd);

hr = rd->putContentHandler(hc);
hr = rd->putErrorHandler(he);
hr = rd->putDTDHandler(hd);
hr = rd->putProperty(L"http://xml.org/sax/properties/lexical-handler", CComVariant(w));
hr = rd->putProperty(L"http://xml.org/sax/properties/declaration-handler", CComVariant(w));

BSTR body = ::SysAllocStringLen(NULL, 1024);
ZeroMemory(body, 1024 * sizeof(OLECHAR));
CComVariant out(body);
w->put_encoding(CComBSTR(L"utf-8"));
hr = w->put_output(out);
hr = rd->parse(CComVariant(dom));

dom->get_xml(&xmlStr);

return std::wstring(xmlStr);

enter image description here

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1 Answer

  1. Editorial Team

    The documentation states that

    Output can be:

    • Any implementation of the IStream interface. (The resulting document will be written into the provided IStream).
    • A string.
    • A DOMDocument object.

    For more information about setting the output property to a DOMDocument object, see Create a DOMDocument Object from SAX Events.

    Setting this property to the empty value (VT_EMPTY or ” “) will return output to the internal string and reset it

    You apparently want the writer to fill the string. So it is suggested to use an empty string to instruct writer to fill its internal buffer and then you can obtain it via property getter.

    You instead attempt to provide your own buffer to be filled, and this is the advertised behavior of the writer.

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