HOWTO: A C++ Sample of ADO Recordset XML Persistence

// 1. ADO Recordset <-> external xml file
// 2. ADO Recordset <-> ADO IStream Object
// 3. ADO Recordset <-> DOM Document

#import "C:\Program files\Common Files\System\Ado\msado15.dll" rename_namespace("MSXML")  rename("EOF", "ADOEOF")

#import "c:\winnt\system32\msxml.dll" 
using namespace MSXML;

#include "stdio.h"
#include "io.h"
void dump_error(_com_error &e) ; //exception handling

void main()
{
	HRESULT hr;
	CoInitialize(NULL);

	try
	{
		//open the connection, get the reocrdset ready
		_ConnectionPtr pConn;
		_RecordsetPtr pRs;
		
		hr = pConn.CreateInstance(__uuidof(Connection));
		hr = pRs.CreateInstance(__uuidof(Recordset));		
	
		pConn->CursorLocation = adUseClient;
		_bstr_t strConn("Provider=sqloledb;Data Source=juliaj01;Initial Catalog=pubs;User Id=<username>;Password=<strong password>;");
		hr = pConn->Open(strConn, "<username>", "<strong password>", adConnectUnspecified);
		hr = pRs->Open("SELECT * from authors", pConn.GetInterfacePtr(), adOpenForwardOnly, adLockReadOnly, adCmdText);
			
		//preparation to save RS as xml file, 
		struct _finddata_t xml_file;
		long hFile;
		if( (hFile = _findfirst("authors.xml", &xml_file )) != -1L)
		{
			DeleteFile("authors.xml"); //if the file exists, delete it
		}

		// 1. Persist it to an external xml file by calling Save with file name and adPersistXML
		hr = pRs->Save("authors.xml", adPersistXML);
		
		// 2. Persist it to ADO IStream Object
		_StreamPtr	pStream ; //declare one first
		pStream.CreateInstance(__uuidof(Stream)); //create it after
		hr = pRs->Save(pStream.GetInterfacePtr(), adPersistXML);    //old trick, call Save 
	
		// 3. Persist it to DOM Document
		IXMLDOMDocumentPtr pXMLDOMDoc; 
		pXMLDOMDoc.CreateInstance(__uuidof(DOMDocument));
		hr = pRs->Save(pXMLDOMDoc.GetInterfacePtr(), adPersistXML);
		// if you want to check out the content call printf(pXMLDOMDoc->Getxml());

		//Recycle the Recordset object
		hr = pRs->Close();

		// 4. load the recordset back from the file by calling Open with MSPersist provider and adCmdFile. 
		// the Recordset will be a ReadOnly, Forwardly only
		hr = pRs->Open("authors.xml","Provider=MSPersist;",adOpenForwardOnly,adLockReadOnly,adCmdFile);
	    	hr = pRs->Close();

		// 5.  Load from IStream object, call Open, first param is pStream.GetInterfacePtr()

		//  Set the steam object position to the beginning of the stream:
		pStream->Position = 0;		

		//  call Open,  passing in vtMissing for connection string, see Q245485 for details
		hr = pRs->Open(pStream.GetInterfacePtr(),vtMissing, adOpenForwardOnly,adLockReadOnly,adCmdFile);
			
		hr = pRs->Close();
		
		// 6 .Load from DOM Document, call Open, first param is pXMLDOMDoc.GetInterfacePtr() and 
		// pass in vtMissing for connection string, see Q245485
		
		hr = pRs->Open(pXMLDOMDoc.GetInterfacePtr(), vtMissing, adOpenForwardOnly, adLockReadOnly, adCmdFile);

		hr = pRs->Close();


		
		//Don't forget to clean up the stream object
		hr = pStream->Close();	
		
	}
	catch(_com_error &e)
	{
		dump_error(e);
	}	
}

void dump_error(_com_error &e)
{
	_bstr_t bstrSource(e.Source());
	_bstr_t bstrDescription(e.Description());
	
	// Print Com errors.  
	printf("Error\n");
	printf("\tCode = %08lx\n", e.Error());
	printf("\tCode meaning = %s", e.ErrorMessage());
	printf("\tSource = %s\n", (LPCSTR) bstrSource);
	printf("\tDescription = %s\n", (LPCSTR) bstrDescription);
	
}