template<class _other_type>  
void QueryInterface(  
   ptr<_other_type> % other  
);  

// comptr_queryinterface.cpp  
// compile with: /clr /link msxml2.lib  
#include <msxml2.h>  
#include <msclr\com\ptr.h>  
  
#import <msxml3.dll> raw_interfaces_only  
  
using namespace System;  
using namespace System::Runtime::InteropServices;  
using namespace msclr;  
  
// a ref class that uses a com::ptr to contain an   
// IXMLDOMDocument object  
ref class XmlDocument {  
public:  
   // construct the internal com::ptr with a null interface  
   // and use CreateInstance to fill it  
   XmlDocument(String^ progid) {  
      m_ptrDoc.CreateInstance(progid);     
   }  
  
   void LoadXml(String^ xml) {  
      pin_ptr<const wchar_t> pinnedXml = PtrToStringChars(xml);  
      BSTR bstr = NULL;  
  
      try {  
         // load some XML into our document  
         bstr = ::SysAllocString(pinnedXml);  
         if (NULL == bstr) {  
            throw gcnew OutOfMemoryException;  
         }  
         VARIANT_BOOL bIsSuccessful = false;  
         // use operator -> to call IXMODOMDocument member function  
         Marshal::ThrowExceptionForHR(m_ptrDoc->loadXML(bstr, &bIsSuccessful));  
      }  
      finally {  
         ::SysFreeString(bstr);  
      }  
   }  
  
   // write the top level node to the console  
   void WriteTopLevelNode() {  
      com::ptr<IXMLDOMNode> ptrNode;  
  
      // query for the top level node interface  
      m_ptrDoc.QueryInterface(ptrNode);  
      WriteNode(ptrNode);  
   }  
  
   // note that the destructor will call the com::ptr destructor  
   // and automatically release the reference to the COM object  
  
private:  
   // simplified function that only writes the node  
   void WriteNode(com::ptr<IXMLDOMNode> % node) {  
      BSTR bstr = NULL;  
  
      try {  
         // write out the name and text properties  
         Marshal::ThrowExceptionForHR(node->get_nodeName(&bstr));  
         String^ strName = gcnew String(bstr);  
         Console::Write("<{0}>", strName);  
         ::SysFreeString(bstr);  
         bstr = NULL;  
  
         Marshal::ThrowExceptionForHR(node->get_text(&bstr));  
         Console::Write(gcnew String(bstr));  
         ::SysFreeString(bstr);  
         bstr = NULL;  
  
         Console::WriteLine("</{0}>", strName);  
      }  
      finally {  
         ::SysFreeString(bstr);  
      }  
   }  
  
   com::ptr<IXMLDOMDocument> m_ptrDoc;  
};  
  
// use the ref class to handle an XML DOM Document object  
int main() {  
   try {  
      // create the class from a progid string  
      XmlDocument doc("Msxml2.DOMDocument.3.0");  
  
      // stream some xml into the document  
      doc.LoadXml("<word>persnickety</word>");  
  
      // write the document to the console  
      doc.WriteTopLevelNode();  
   }  
   catch (Exception^ e) {  
      Console::WriteLine(e);     
   }  
}  

<#document>persnickety</#document>