Peeking at MSMQ queues

Hi. I'm trying out the MSMQ API using VC++ v6 on NT4. I have written the following code, and I seem to be managing to both open and peek at the queue, but I don't get intelligible responses when trying to display the message label and body...

Code:

---

void CReadMSMQDlg::OnRead()
{
        HRESULT hr = S_OK;
        IMSMQQueuePtr pQueue;                        // The pointer to the queue (contents level)
        CString msg;

        try
        {
                IMSMQQueueInfoPtr pInfo("MSMQ.MSMQQueueInfo"); // The pointer to the queue itself

                pInfo->FormatName = "DIRECT=TCP:IPAddress\\QName";

                // Open the queue for receive access
                pQueue = pInfo->Open( MQ_PEEK_ACCESS, MQ_DENY_NONE );

                IMSMQMessagePtr pMsg("MSMQ.MSMQMessage");

                _variant_t vtTimeOut((long)1000);  // 1 second until receive time-out
                _variant_t bvtWantBody((bool)true); // Set to retrieve message body

                // Read all the messages in queue until 1 second time-out
                for( ;; )
                {
                        pMsg = pQueue->Peek( &vtMissing, &bvtWantBody, &vtTimeOut );

                        if( pMsg == NULL )
                        {
                                msg.Format( "No messages on %s", pInfo->FormatName );
                                MessageBox( msg, NULL, MB_OK );
                                pQueue->Close();
                                pQueue = NULL;
                                break;
                        }

                        // Display the message label and body
                        msg.Format( "%s", pMsg->Label );
                        //msg.Format( "%s", pMsg->Body );

                        MessageBox( "DEBUG Label", msg, MB_OK );
                }
        }
        catch( const _com_error& comerr )
        {
                hr = comerr.Error();
                msg.Format( "Error Code = 0x%X", hr );
                MessageBox( msg, "COM ERR", MB_OK );
               
                msg.Format( "Error Description = %s", (WCHAR *)comerr.Description() );
                MessageBox( msg, "COM ERR", MB_OK );               

                if( pQueue )
                        pQueue->Close();
        }
}

---

From looking on MSDN, Label is supposed to be a string, but it doesn't display the message label I'd expect, and is just showing rubbish really. Also, MSDN says that the body variable is a 'variant', does anybody know how too handle this data type?

Thanks.

A COM string with an #import generated framework is represented as a _bstr_t class.

Code:

---

msg.Format( "%s", pMsg->Label );

---

Passing a class or structure such as a _bstr_t to a variable args function is an unreliable operation. You need to use one of the _bstr_t cast operators to get a simple(or POD) type.

Code:

---

msg.Format( "%s", (char*) pMsg->Label );
// or
msg.Format( "%S", (wchar_t*) pMsg->Label );

---

Similarly, a _variant_t can be cast to a _bstr_t which can then be cast to char* or wchar_t*:

Code:

---

msg.Format( "%s", (char*) (_bstr_t) pMsg->Body );

---

C++ style casts would be stylistically preferable.

All my problems solved.

Thankyou.