c ++中的Xpath查询(Xpath Query in c++)

 我需要在C ++中使用xpath查询来直接从节点<revisions>获取idNumber 。 我尝试了以下内容，它总是返回null 。 请让我知道我做错了什么。 
 
 xml文件： 
 
<?xml version="1.0" encoding="UTF-8" ?>

<cw:vessel version="1.07.0075" creationDate="2016-01-26" xmlns:cw="urn:container">
    <!-- saved from url=(0024)http://www.systemsoftsol.com/ -->
    <Exchanger>
        <revisions>
            <revision>
               <idNumber>1401889476</idNumber>
               <revNumber>0</revNumber>
               <revDate>2014-06-04</revDate>
               <operator>devin</operator>
               <notes>read me</notes>
            </revision>
        </revisions>
  </Exchanger>
</cw:vessel>
 
 我的代码到目前为止： 
 
void GetProperties()
{
    HRESULT                         hr = NOERROR;
    CComPtr<::IXMLDOMDocument3>     m_pxmlDomDocument = NULL;
    CComPtr<::IXMLDOMNode>          pNode = NULL;
    IXMLDOMNodeList*                pChildlist = NULL;
    VARIANT_BOOL                    vLoadBool = VARIANT_FALSE;
    hr = m_pxmlDomDocument.CoCreateInstance(__uuidof(DOMDocument60));
    hr = m_pxmlDomDocument->setProperty(BSTR(L"SelectionLanguage"), (CComVariant)L"XPath");
    hr = m_pxmlDomDocument->setProperty((CComBSTR)"MaxElementDepth", (CComVariant)INT_MAX);
    if (FAILED(hr))
    {
        hr = ERROR_XML_PARSE_ERROR;
    }
    CComVariant varXmlFileName(_T("xmlfileinput"));
    m_pxmlDomDocument->load(varXmlFileName, &vLoadBool);
    hr = m_pxmlDomDocument->get_documentElement(&pDocRoot);
    hr = pDocRoot->selectSingleNode(_T("//Exchanger"), &pNode);
    pNode->get_childNodes(&pChildlist);
    long size;
    hr = pChildlist->get_length(&size);
    for (int i = 0; i < size; i++)
    {
        CComPtr<::IXMLDOMNode> referNode;
        hr = pChildlist->get_item(i, &referNode);
        if (referNode != NULL)
        {
            CString         csXPathQuery;
            csXPathQuery.Append(_T("/idNumber"));// i need this from above xml
            CComBSTR                    csBstrQuery(csXPathQuery);
            CComPtr<::IXMLDOMNode> pPa;
            hr = referNode->selectSingleNode(csBstrQuery.m_str, &pPa);
        }
    }
}   
 
 selectSingleNode()在上面的代码片段中返回null ，即使我在xml文件中仍然有idNumber 。 

I need a xpath query in C++ to get the idNumber directly from the node <revisions>. I tried the following and it always returns null. Please let me know what I am doing wrong. 
 
xml File:
 
<?xml version="1.0" encoding="UTF-8" ?>

<cw:vessel version="1.07.0075" creationDate="2016-01-26" xmlns:cw="urn:container">
    <!-- saved from url=(0024)http://www.systemsoftsol.com/ -->
    <Exchanger>
        <revisions>
            <revision>
               <idNumber>1401889476</idNumber>
               <revNumber>0</revNumber>
               <revDate>2014-06-04</revDate>
               <operator>devin</operator>
               <notes>read me</notes>
            </revision>
        </revisions>
  </Exchanger>
</cw:vessel>
 
My code so far:
 
void GetProperties()
{
    HRESULT                         hr = NOERROR;
    CComPtr<::IXMLDOMDocument3>     m_pxmlDomDocument = NULL;
    CComPtr<::IXMLDOMNode>          pNode = NULL;
    IXMLDOMNodeList*                pChildlist = NULL;
    VARIANT_BOOL                    vLoadBool = VARIANT_FALSE;
    hr = m_pxmlDomDocument.CoCreateInstance(__uuidof(DOMDocument60));
    hr = m_pxmlDomDocument->setProperty(BSTR(L"SelectionLanguage"), (CComVariant)L"XPath");
    hr = m_pxmlDomDocument->setProperty((CComBSTR)"MaxElementDepth", (CComVariant)INT_MAX);
    if (FAILED(hr))
    {
        hr = ERROR_XML_PARSE_ERROR;
    }
    CComVariant varXmlFileName(_T("xmlfileinput"));
    m_pxmlDomDocument->load(varXmlFileName, &vLoadBool);
    hr = m_pxmlDomDocument->get_documentElement(&pDocRoot);
    hr = pDocRoot->selectSingleNode(_T("//Exchanger"), &pNode);
    pNode->get_childNodes(&pChildlist);
    long size;
    hr = pChildlist->get_length(&size);
    for (int i = 0; i < size; i++)
    {
        CComPtr<::IXMLDOMNode> referNode;
        hr = pChildlist->get_item(i, &referNode);
        if (referNode != NULL)
        {
            CString         csXPathQuery;
            csXPathQuery.Append(_T("/idNumber"));// i need this from above xml
            CComBSTR                    csBstrQuery(csXPathQuery);
            CComPtr<::IXMLDOMNode> pPa;
            hr = referNode->selectSingleNode(csBstrQuery.m_str, &pPa);
        }
    }
}   
 
selectSingleNode() returns null in the above piece of code even though I still have the idNumber in the xml file.

原文：https://stackoverflow.com/questions/35580202