R., K.,
I have managed to create a C++ example with ReadMultipleItems and DAVtqResult at this last moment.

Here is a code that works (tested with QuickOPC-COM 5.10):

#include "stdafx.h"
#include 
#include 
 
#import "libid:FAB7A1E3-3B79-4292-9C3A-DF39A6F65EC1" version(5.1)    // EasyOpcLib
using namespace EasyOpcLib;
 
int _tmain(int argc, _TCHAR* argv[])
{
       // Initialize the COM library
       CoInitialize(NULL);
 
       // Instatiate the EasyOPC-DA client object
       IEasyDAClientPtr EasyDAClientPtr(__uuidof(EasyDAClient));
 
       CComSafeArray ItemIdArray(4);
       ItemIdArray[0] = _T("Simulation.Random");
       ItemIdArray[1] = _T("Trends.Ramp (1 min)");
       ItemIdArray[2] = _T("Trends.Sine (1 min)");
       ItemIdArray[3] = _T("Simulation.Register_I4");
 
       CComVariant vMissing;
       vMissing.vt = VT_ERROR;
 
       CComVariant vResults(EasyDAClientPtr->ReadMultipleItems(_T(""), _T("OPCLabs.KitServer.2"), 
              CComVariant(ItemIdArray.Detach()), vMissing));
 
       CComSafeArray ResultArray(vResults.parray);
       for (int i = ResultArray.GetLowerBound(0); i < ResultArray.GetUpperBound(0); i++)
       {
              IDAVtqResultPtr DAVtqResultPtr(ResultArray);
              IDAVtqPtr DAVtqPtr(DAVtqResultPtr->Vtq);
              _tprintf(_T("results(%d).Vtq.ToString(): %s\n"), i, DAVtqPtr->ToString().bstrVal);
       }
 
       // Release all interface pointers BEFORE calling CoUninitialize()
       ResultArray.Destroy();
       vResults.Clear();
       EasyDAClientPtr = NULL;
 
       CoUninitialize();
 
       TCHAR line[80];
       _putts(_T("Press Enter to continue..."));
       _fgetts(line, sizeof(line), stdin);
       return 0;
}


I am attaching a zipped project, too (in VS 2010).
If the customer is using managed C++ with QuickOPC.NET, the code would be quite different, though; in such case, let me know again.

Best regards,

From: R.
Sent: Thursday, June 30, 2011 6:35 PM
To: Zbynek Zahradnik
Subject: C++ ReadMultipleItems example

Hello Zbynek,
I have a customer who is having trouble with the ReadMultipleItems callback using C++. He said he is getting some errors about the DaVTQResult being an invalid structure?

Do you have any quick examples that demonstrate this method?

Thanks,
R.