Creating a Disconnected Recordset in C++ For VB

Environment: Visual C++ 6.0 and VB 6.0, ADO 1.5

This article assumes that you are familiar with ADO, Visual C++ and ATL.

This article shows how to create a Visual C++ COM object that creates a disconnected ADO Recordset. With a disconnected ADO recordset, your ATL COM object can connect to the database, create the Recordset, and disconnect without having to keep a connection open, while allowing the client to read the data in the Recordset. This works great with MTS where database connection pooling requires this functionality.

Resources: HOWTO: Getting ADO Disconnected Recordsets in VBA/C++/Java
SAMPLE: ATL2ADO.exe Returns Disconnected ADO Recordset

In your project make sure you import dll to create your ADO classes.

#import "c:\program files\common files\system\ado\msado15.dll" no_namespace rename("EOF", "adoEOF") implementation_only

Next create a method with an [out, retval] property of type _Recordset **

[id(1), helpstring("method GetADORecordset")] HRESULT GetADORecordset( [out, retval] _Recordset **ppRecordset);

Your source code should look something like this:

STDMETHODIMP CReturnADO::GetADORecordset(_Recordset **ppRecordset)
	_ConnectionPtr	pConnection;
	_RecordsetPtr	pRecordset;
		pConnection->CursorLocation = adUseClient; // Important for disconnected sets

		pRecordset->CursorLocation = adUseClient; // Important for disconnected sets
		pRecordset->PutRefActiveConnection(pConnection.GetInterfacePtr()); // Associate the connection to this recordset

		pRecordset->Open("SELECT DISTINCT name FROM TBLWHATEVER WHERE name IS NOT NULL",vtMissing,
			adOpenForwardOnly, adLockReadOnly,

        pRecordset->PutRefActiveConnection(NULL); // Disassociate the connection from the recordset.

		if(pConnection->GetState() == adStateOpen)
		pConnection = NULL;
		*ppRecordset = pRecordset.Detach();

	catch(_com_error *e)
		return AtlReportError(CLSID_ReturnADO,e->ErrorMessage(),IID_IReturnADO,E_FAIL);
		return AtlReportError(CLSID_ReturnADO,"Unknown Error.",IID_IReturnADO,E_FAIL);

	return S_OK;

Now your interface descriptions and CLSID's will be different, but go ahead and use this code to build your own version. Your VB code might look something like this:

    Dim adoset As ADODB.Recordset
    Dim engine As New TESTRETURNADOLib.ReturnADO
    Set adoset = engine.GetADORecordset
    While Not adoset.EOF
        List1.AddItem adoset.Fields(0)
    Set adoset = Nothing


  • There are no comments yet. Be the first to comment!

Leave a Comment
  • Your email address will not be published. All fields are required.

Top White Papers and Webcasts

  • Moving from an on-premises environment to Office 365 does not remove the need to plan for disruptions or reduce the business risk requirements for protecting email services. If anything, some risks increase with a move to the cloud. Read how to ease the transition every business faces if considering or already migrating to cloud email. This white paper discusses: Setting expectations when migrating to Office 365 Understanding the implications of relying solely on Exchange Online security Necessary archiving …

  • Lenovo recommends Windows 8 Pro. "I dropped my laptop getting out of the taxi." This probably sounds familiar to most IT professionals. If your employees are traveling, you know their devices are in for a rough go. Whether it's a trip to the conference room or a convention out of town, any time equipment leaves a user's desk it is at risk of being put into harm's way. Stay connected at all times, whether at the office or on the go, with agile, durable, and flexible devices like the Lenovo® …

Most Popular Programming Stories

More for Developers

RSS Feeds

Thanks for your registration, follow us on our social networks to keep up-to-date