#include <iostream>
#include <tchar.h>

#import <msxml3.dll>

//节点处理函数
void ProcessNode(MSXML2::IXMLDOMNodePtr spNode)
{
std::cout << "nodeName: " << spNode->nodeName;
if (spNode->nodeType == NODE_ATTRIBUTE || spNode->nodeType == NODE_TEXT)
std::cout << "\tnodeValue: " << _bstr_t(spNode->nodeValue);
std::cout << std::endl;

if (spNode->nodeType == NODE_ELEMENT)
{
MSXML2::IXMLDOMNamedNodeMapPtr spNameNodeMap = spNode->attributes;
for (long i = 0; i != spNameNodeMap->length; ++i) //遍历节点属性
ProcessNode(spNameNodeMap->item[i]);

MSXML2::IXMLDOMNodeListPtr spNodeList = spNode->childNodes;
for (long i = 0; i != spNodeList->length; ++i) //遍历子节点
ProcessNode(spNodeList->item[i]);
}
}

int _tmain(int argc, _TCHAR* argv[])
{
CoInitialize(NULL);
//读取XML
MSXML2::IXMLDOMDocumentPtr spXMLDoc;
spXMLDoc.CreateInstance(__uuidof(MSXML2::DOMDocument30));
spXMLDoc->load(L"stocks.xml");
MSXML2::IXMLDOMElementPtr spRoot = spXMLDoc->documentElement; //根节点
MSXML2::IXMLDOMNodeListPtr spNodeList = spRoot->childNodes;
for (long i = 0; i != spNodeList->length; ++i) //遍历子节点
ProcessNode(spNodeList->item[i]);

//写入XML
spRoot->selectSingleNode(L"/root/node1")->text = L"newText";
spRoot->selectSingleNode(L"/root/node2/childnode1/@attrib1")->nodeValue = L"newValue";
MSXML2::IXMLDOMNodePtr spNewNode = spRoot->selectSingleNode(L"/root/node2")->appendChild(
spXMLDoc->createNode(_variant_t(NODE_ELEMENT), L"childnode3", L"")
); //给node2创建新子节点childnode3
spNewNode->text = L"childtext2";
MSXML2::IXMLDOMElementPtr spEle = spNewNode;
spEle->setAttribute(L"attrib1", _variant_t(L"value1")); //添加新属性
spXMLDoc->save(_variant_t(L"stocks.xml"));

spNewNode.Release();
spEle.Release();
spNodeList.Release();
spRoot.Release();
spXMLDoc.Release();
CoUninitialize();

system("pause");
return 0;
}

MFC
MFC里可以直接使用DOM，不需要手动添加额外的头文件，只需要在CWinApp::InitInstance()里调用CoInitialize(NULL)初始化COM，在CWinApp::ExitInstance里调用CoUninitialize()释放COM就行了。

//读取XML
CComPtr<IXMLDOMDocument> spDoc; //DOM
spDoc.CoCreateInstance(CLSID_DOMDocument);
VARIANT_BOOL vb;
spDoc->load(CComVariant(OLESTR("stocks.xml")), &vb); //加载XML文件
CComPtr<IXMLDOMElement> spRootEle;
spDoc->get_documentElement(&spRootEle); //根节点
CComPtr<IXMLDOMNodeList> spNodeList;
spRootEle->get_childNodes(&spNodeList); //子节点列表
long nLen;
spNodeList->get_length(&nLen); //子节点数
for (long i = 0; i != nLen; ++i) //遍历子节点
{
CComPtr<IXMLDOMNode> spNode;
spNodeList->get_item(i, &spNode);
ProcessNode(spNode); //节点处理函数
}

//写入XML
CComPtr<IXMLDOMNode> spNode;
spRootEle->selectSingleNode(OLESTR("/root/node1"), &spNode);
spNode->put_text(OLESTR("newText")); //写入text
spRootEle->selectSingleNode(OLESTR("/root/node2/childnode1/@attrib1"), &spNode);
spNode->put_nodeValue(CComVariant(OLESTR("newValue"))); //写入value
CComPtr<IXMLDOMNode> spNewNode;
spDoc->createNode(CComVariant(NODE_ELEMENT), OLESTR("childnode3"), OLESTR(""), &spNewNode); //创建新节点
spRootEle->selectSingleNode(OLESTR("/root/node2"), &spNode);
spNode->appendChild(spNewNode, &spNewNode); //将新节点加为node2的子节点
spNewNode->put_text(OLESTR("childtext2")); //写入新节点text
CComQIPtr<IXMLDOMElement> spEle = spNewNode; //注意这里使用CComQIPtr
spEle->setAttribute(OLESTR("attrib1"), CComVariant(OLESTR("value1")));//给新节点添加属性
spDoc->save(CComVariant(OLESTR("stocks.xml")));

//节点处理函数
void ProcessNode(CComPtr<IXMLDOMNode>& spNode)
{
CComBSTR bsNodeName;
spNode->get_nodeName(&bsNodeName); //节点名
AfxMessageBox(COLE2CT(bsNodeName));
CComVariant varVal;
spNode->get_nodeValue(&varVal); //节点值
AfxMessageBox(COLE2CT(varVal.bstrVal));

DOMNodeType eNodeType;
spNode->get_nodeType(&eNodeType);
if (eNodeType == NODE_ELEMENT) //只有NODE_ELEMENT类型才能包含有属性和子节点
{
//递归遍历节点属性
CComPtr<IXMLDOMNamedNodeMap> spNameNodeMap;
spNode->get_attributes(&spNameNodeMap);
long nLength;
spNameNodeMap->get_length(&nLength);
for (long i = 0; i != nLength; ++i)
{
CComPtr<IXMLDOMNode> spNodeAttrib; //注意属性也是一个IXMLDOMNode
spNameNodeMap->get_item(i, &spNodeAttrib);
ProcessNode(spNodeAttrib);
}

//递归遍历子节点
CComPtr<IXMLDOMNodeList> spNodeList;
spNode->get_childNodes(&spNodeList);
spNodeList->get_length(&nLength);
for (long i = 0; i != nLength; ++i)
{
CComPtr<IXMLDOMNode> spChildNode;
spNodeList->get_item(i, &spChildNode);
ProcessNode(spChildNode);
}
}
}

对于text这样的节点，get_nodeValue会得到空，要得到"text"的话可以遍历子节点（只有一个子节点，它的nodeName为"#text"，nodeType为NODE_TEXT，nodeValue就是"text"）；也可以用get_text直接得到"text"，但是对于这样的节点textchildtext，get_text会同时得到"text"和"childtext"，不过这样的节点应该是不允许的。
DOM里使用的字符串(BSTR)都是OLESTR类型，默认情况下OLESTR是Unicode字符，MFC里可以用COLE2CT把LPCOLESTR转换为LPCTSTR。
对于自己定义的XML，大多数时候不需要遍历，可以通过调用selectNodes、selectSingleNode指定XPath直接读取某个节点或属性：

CComPtr<IXMLDOMDocument> spDoc; //DOM
spDoc.CoCreateInstance(CLSID_DOMDocument);
VARIANT_BOOL vb;
spDoc->load(CComVariant(OLESTR("stocks.xml")), &vb); //加载XML文件
CComPtr<IXMLDOMElement> spRootEle;
spDoc->get_documentElement(&spRootEle); //根节点

CComPtr<IXMLDOMNodeList> spNodeList;
CComPtr<IXMLDOMNode> spNode;
spRootEle->selectNodes(OLESTR("/root/node2/*"), &spNodeList); //得到node2下的所有子节点
spRootEle->selectSingleNode(OLESTR("/root/node2/childnode1/@attrib1"), &spNode); //得到childnode1的attrib1属性

XPath的语法可以参考XML文档或MSDN。

最后放上xml

<?xml version="1.0" encoding="utf-8"?>
<root>
<node1>text1</node1>
<node2>
<childnode1 attrib1="value1" attrib2="value2"/>
<childnode2 attrib1="value1" attrib2="value2">childtext1</childnode2>
</node2>
</root>