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EricMEvans · 23 Sep 2002

Anyone here dealt with event trapping in C++? I keep getting a Catastrophic Error on my friggin' Advise statement.

I'm trying to trap the event of an ADO connection object.

Acid · 06 Jun 2002

I can't seem to find anything on it. It say, make it impossible for the user to make the error in the first place. eg check if the number they gave actually is a number before continuing. But I can't find any "on error do this" code. hehe, VB is so much simpler.

EricMEvans · 23 Sep 2002

I'm trying to trap when the database goes down otherwise the dll just hangs. A solution someone did in the past doubled the processing time.

Yes, VB is A LOT easier when it comes to events.

Acid · 06 Jun 2002

maybe try reading a short thing from the database, if it can, then do the rest if it can't them you know the connection is down. or will this also hand the .dll?

EricMEvans · 23 Sep 2002

I hangs when trying to do the actual connection. You'd think the stupid connection object would just bail but it doesn't.

Acid · 06 Jun 2002

how can the db go down anyways, is it online?

EricMEvans · 23 Sep 2002

If something like a router went down, the connection could be lost. This isn't an app for personal use. This is a widely used database connection manager dll we use here at Anheuser-Busch (the people that make Budweiser). For some reason they like failsafe applications and stuff.

Acid · 06 Jun 2002

I've asked on another forum, I'll post any replies.

EricMEvans · 23 Sep 2002

Thank ya!

Acid · 06 Jun 2002

Here's the thread:
http://vbforums.com/showthread.php?s=&threadid=287501

He's expecting you to post some code. Don't ask me what code.

EricMEvans · 23 Sep 2002

Here is some of my code. m_pAdoCon is my ADO connection object. After I create the hADOEventHandle I pass it to WaitForSingleObject where the code waits for the connect to fire.

It would work but it yarfs on my Advise statement.

This code is based upon the ado event trapping example in MSDN.

***.CPP

Code:

DWORD dwConnEvt = NULL;
IConnectionPointContainer *pCPC = NULL;
IConnectionPoint *pCP = NULL;
IUnknown *pUnk = NULL;
CConnEvent *pConnEvent= NULL;
int rc = 0;

//ConnectComplete Event for ADO
STDMETHODIMP CConnEvent::raw_ConnectComplete(
struct Error *pError,
ADODB::EventStatusEnum *adStatus,
struct _Connection *pConnection)
{
   *adStatus = ADODB::adStatusOK;
   SetEvent(hADOEventHandle); //Set the event handle
   return S_OK;
};

//Disconnect Event for ADO
STDMETHODIMP CConnEvent::raw_Disconnect(
ADODB::EventStatusEnum *adStatus,
struct _Connection *pConnection)
{
   *adStatus = ADODB::adStatusUnwantedEvent;
   return S_OK;
};

//QueryInterface Function for CConnEvent
STDMETHODIMP CConnEvent::QueryInterface(REFIID riid, void ** ppv)
{
*ppv = NULL;
if (riid == __uuidof(IUnknown) ||
riid == __uuidof(ADODB::ConnectionEventsVt)) *ppv = this;
if (*ppv == NULL)
return ResultFromScode(E_NOINTERFACE);
AddRef();
return NOERROR;
}

STDMETHODIMP_(ULONG) CConnEvent::AddRef() { return ++m_cRef; };

STDMETHODIMP_(ULONG) CConnEvent::Release()
{
if (0 != --m_cRef) return m_cRef;
   delete this;
return 0;
}

......
......

//QueryInterface function is overridden and up above in this code
hr = m_pAdoCon->QueryInterface(__uuidof(IConnectionPointContainer), (void **)&pCPC);
if (FAILED(hr)) return rc;

hr = pCPC->FindConnectionPoint(__uuidof(ADODB::ConnectionEvents), &pCP);
pCPC->Release();
if (FAILED(hr)) return rc;

pConnEvent = new CConnEvent();
hr = pConnEvent->QueryInterface(__uuidof(IUnknown), (void **) &pUnk);
if (FAILED(hr)) return rc;

hr = pCP->Advise(pUnk, &dwConnEvt);
pCP->Release();
if (FAILED(hr)) return rc;

//hADOEventHandle gets set in the raw_ConnectComplete event
pConnEvent->hADOEventHandle = CreateEvent(NULL, false, false, NULL);
if(pConnEvent->hADOEventHandle == NULL)
CBUDNETStdException::BUDNETThrowException(E_FAIL,"Could not open connection.", BudNETMessage);

***.H

Code:

class CConnEvent :
public CComCoClass<ADODB::ConnectionEventsVt>
{
private:
ULONG m_cRef;

public:
CConnEvent() { m_cRef = 0; };
~CConnEvent() {};
HANDLE hADOEventHandle;
STDMETHODIMP QueryInterface(REFIID riid, void ** ppv);
STDMETHODIMP_(ULONG) AddRef(void);
STDMETHODIMP_(ULONG) Release(void);

STDMETHODIMP raw_ConnectComplete(struct Error *pError, ADODB::EventStatusEnum *adStatus, struct _Connection *pConnection);
STDMETHODIMP raw_Disconnect(ADODB::EventStatusEnum *adStatus, struct _Connection *pConnection);
};

Thanks for any help you can provide!

Acid · 06 Jun 2002

OK, the other forum is stumped.
Sorry about that.

batfink · 25 Jan 2003

Eric are you sure the Advise method has two arguementss? You have pUnk & & dwConnEvt, should there only be one arguement here?

Code:

hr = pCP->Advise(pUnk, &dwConnEvt);

batfink · 25 Jan 2003

ok maybe as many as you like...ignore me.

cyclops

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/ado270/htm/mdevteventmodelxvc.asp

EricMEvans · 23 Sep 2002

Well then they are a bunch of poop heads