ADO Events Model Example (VC++)
The Visual C++ section of ADO Event Instantiation by Language gives a general description of how to instantiate the ADO event model. The following is a specific example of instantiating the event model within the environment created by the #import directive.
The general description uses adoint.h as a reference for method signatures. However, a few details in the general description change slightly as a result of using the #import directive:
- The #import directive resolves typedef's, and method signature data types and modifiers to their fundamental forms.
- The pure virtual methods that must be overwritten are all prefixed by "raw_".
Some of the code simply reflects coding style.
- The pointer to IUnknown used by the Advise method is obtained explicitly with a call to QueryInterface.
- You don't need to explicitly code a destructor in the class definitions.
- You may want to code more robust implementations of QueryInterface, AddRef, and Release.
- The __uuidof() directive is used extensively to obtain interface IDs.
Finally, the example contains some working code.
- The example is written as a console application.
- You should insert your own code under the comment, "
// Do some work". - All the event handlers default to doing nothing, and canceling further notifications. You should insert the appropriate code for your application, and allow notifications if required.
// eventmodel.cpp : Defines the entry point for the console application.
//
#import "c:\Program Files\Common Files\System\ADO\msado15.dll" \
no_namespace rename("EOF", "EndOfFile")
#include <comdef.h>
#include <stdio.h>
//----The Connection events----------------------------------------------
class CConnEvent : public ConnectionEventsVt
{
private:
ULONG m_cRef;
public:
CConnEvent() { m_cRef = 0; };
~CConnEvent() {};
STDMETHODIMP QueryInterface(REFIID riid, void ** ppv);
STDMETHODIMP_(ULONG) AddRef(void);
STDMETHODIMP_(ULONG) Release(void);
STDMETHODIMP raw_InfoMessage(
struct Error *pError,
EventStatusEnum *adStatus,
struct _Connection *pConnection);
STDMETHODIMP raw_BeginTransComplete(
LONG TransactionLevel,
struct Error *pError,
EventStatusEnum *adStatus,
struct _Connection *pConnection);
STDMETHODIMP raw_CommitTransComplete(
struct Error *pError,
EventStatusEnum *adStatus,
struct _Connection *pConnection);
STDMETHODIMP raw_RollbackTransComplete(
struct Error *pError,
EventStatusEnum *adStatus,
struct _Connection *pConnection);
STDMETHODIMP raw_WillExecute(
BSTR *Source,
CursorTypeEnum *CursorType,
LockTypeEnum *LockType,
long *Options,
EventStatusEnum *adStatus,
struct _Command *pCommand,
struct _Recordset *pRecordset,
struct _Connection *pConnection);
STDMETHODIMP raw_ExecuteComplete(
LONG RecordsAffected,
struct Error *pError,
EventStatusEnum *adStatus,
struct _Command *pCommand,
struct _Recordset *pRecordset,
struct _Connection *pConnection);
STDMETHODIMP raw_WillConnect(
BSTR *ConnectionString,
BSTR *UserID,
BSTR *Password,
long *Options,
EventStatusEnum *adStatus,
struct _Connection *pConnection);
STDMETHODIMP raw_ConnectComplete(
struct Error *pError,
EventStatusEnum *adStatus,
struct _Connection *pConnection);
STDMETHODIMP raw_Disconnect(
EventStatusEnum *adStatus,
struct _Connection *pConnection);
};
//-----The Recordset events----------------------------------------------
class CRstEvent : public RecordsetEventsVt
{
private:
ULONG m_cRef;
public:
CRstEvent() { m_cRef = 0; };
~CRstEvent() {};
STDMETHODIMP QueryInterface(REFIID riid, void ** ppv);
STDMETHODIMP_(ULONG) AddRef(void);
STDMETHODIMP_(ULONG) Release(void);
STDMETHODIMP raw_WillChangeField(
LONG cFields,
VARIANT Fields,
EventStatusEnum *adStatus,
struct _Recordset *pRecordset);
STDMETHODIMP raw_FieldChangeComplete(
LONG cFields,
VARIANT Fields,
struct Error *pError,
EventStatusEnum *adStatus,
struct _Recordset *pRecordset);
STDMETHODIMP raw_WillChangeRecord(
EventReasonEnum adReason,
LONG cRecords,
EventStatusEnum *adStatus,
struct _Recordset *pRecordset);
STDMETHODIMP raw_RecordChangeComplete(
EventReasonEnum adReason,
LONG cRecords,
struct Error *pError,
EventStatusEnum *adStatus,
struct _Recordset *pRecordset);
STDMETHODIMP raw_WillChangeRecordset(
EventReasonEnum adReason,
EventStatusEnum *adStatus,
struct _Recordset *pRecordset);
STDMETHODIMP raw_RecordsetChangeComplete(
EventReasonEnum adReason,
struct Error *pError,
EventStatusEnum *adStatus,
struct _Recordset *pRecordset);
STDMETHODIMP raw_WillMove(
EventReasonEnum adReason,
EventStatusEnum *adStatus,
struct _Recordset *pRecordset);
STDMETHODIMP raw_MoveComplete(
EventReasonEnum adReason,
struct Error *pError,
EventStatusEnum *adStatus,
struct _Recordset *pRecordset);
STDMETHODIMP raw_EndOfRecordset(
VARIANT_BOOL *fMoreData,
EventStatusEnum *adStatus,
struct _Recordset *pRecordset);
STDMETHODIMP raw_FetchProgress(
long Progress,
long MaxProgress,
EventStatusEnum *adStatus,
struct _Recordset *pRecordset);
STDMETHODIMP raw_FetchComplete(
struct Error *pError,
EventStatusEnum *adStatus,
struct _Recordset *pRecordset);
};
//-----Implement each connection method----------------------------------
STDMETHODIMP CConnEvent::raw_InfoMessage(
struct Error *pError,
EventStatusEnum *adStatus,
struct _Connection *pConnection)
{
*adStatus = adStatusUnwantedEvent;
return S_OK;
};
STDMETHODIMP CConnEvent::raw_BeginTransComplete(
LONG TransactionLevel,
struct Error *pError,
EventStatusEnum *adStatus,
struct _Connection *pConnection)
{
*adStatus = adStatusUnwantedEvent;
return S_OK;
};
STDMETHODIMP CConnEvent::raw_CommitTransComplete(
struct Error *pError,
EventStatusEnum *adStatus,
struct _Connection *pConnection)
{
*adStatus = adStatusUnwantedEvent;
return S_OK;
};
STDMETHODIMP CConnEvent::raw_RollbackTransComplete(
struct Error *pError,
EventStatusEnum *adStatus,
struct _Connection *pConnection)
{
*adStatus = adStatusUnwantedEvent;
return S_OK;
};
STDMETHODIMP CConnEvent::raw_WillExecute(
BSTR *Source,
CursorTypeEnum *CursorType,
LockTypeEnum *LockType,
long *Options,
EventStatusEnum *adStatus,
struct _Command *pCommand,
struct _Recordset *pRecordset,
struct _Connection *pConnection)
{
*adStatus = adStatusUnwantedEvent;
return S_OK;
};
STDMETHODIMP CConnEvent::raw_ExecuteComplete(
LONG RecordsAffected,
struct Error *pError,
EventStatusEnum *adStatus,
struct _Command *pCommand,
struct _Recordset *pRecordset,
struct _Connection *pConnection)
{
*adStatus = adStatusUnwantedEvent;
return S_OK;
};
STDMETHODIMP CConnEvent::raw_WillConnect(
BSTR *ConnectionString,
BSTR *UserID,
BSTR *Password,
long *Options,
EventStatusEnum *adStatus,
struct _Connection *pConnection)
{
*adStatus = adStatusUnwantedEvent;
return S_OK;
};
STDMETHODIMP CConnEvent::raw_ConnectComplete(
struct Error *pError,
EventStatusEnum *adStatus,
struct _Connection *pConnection)
{
*adStatus = adStatusUnwantedEvent;
return S_OK;
};
STDMETHODIMP CConnEvent::raw_Disconnect(
EventStatusEnum *adStatus,
struct _Connection *pConnection)
{
*adStatus = adStatusUnwantedEvent;
return S_OK;
};
//-----Implement each recordset method-----------------------------------
STDMETHODIMP CRstEvent::raw_WillChangeField(
LONG cFields,
VARIANT Fields,
EventStatusEnum *adStatus,
struct _Recordset *pRecordset)
{
*adStatus = adStatusUnwantedEvent;
return S_OK;
};
STDMETHODIMP CRstEvent::raw_FieldChangeComplete(
LONG cFields,
VARIANT Fields,
struct Error *pError,
EventStatusEnum *adStatus,
struct _Recordset *pRecordset)
{
*adStatus = adStatusUnwantedEvent;
return S_OK;
};
STDMETHODIMP CRstEvent::raw_WillChangeRecord(
EventReasonEnum adReason,
LONG cRecords,
EventStatusEnum *adStatus,
struct _Recordset *pRecordset)
{
*adStatus = adStatusUnwantedEvent;
return S_OK;
};
STDMETHODIMP CRstEvent::raw_RecordChangeComplete(
EventReasonEnum adReason,
LONG cRecords,
struct Error *pError,
EventStatusEnum *adStatus,
struct _Recordset *pRecordset)
{
*adStatus = adStatusUnwantedEvent;
return S_OK;
};
STDMETHODIMP CRstEvent::raw_WillChangeRecordset(
EventReasonEnum adReason,
EventStatusEnum *adStatus,
struct _Recordset *pRecordset)
{
*adStatus = adStatusUnwantedEvent;
return S_OK;
};
STDMETHODIMP CRstEvent::raw_RecordsetChangeComplete(
EventReasonEnum adReason,
struct Error *pError,
EventStatusEnum *adStatus,
struct _Recordset *pRecordset)
{
*adStatus = adStatusUnwantedEvent;
return S_OK;
};
STDMETHODIMP CRstEvent::raw_WillMove(
EventReasonEnum adReason,
EventStatusEnum *adStatus,
struct _Recordset *pRecordset)
{
*adStatus = adStatusUnwantedEvent;
return S_OK;
};
STDMETHODIMP CRstEvent::raw_MoveComplete(
EventReasonEnum adReason,
struct Error *pError,
EventStatusEnum *adStatus,
struct _Recordset *pRecordset)
{
*adStatus = adStatusUnwantedEvent;
return S_OK;
};
STDMETHODIMP CRstEvent::raw_EndOfRecordset(
VARIANT_BOOL *fMoreData,
EventStatusEnum *adStatus,
struct _Recordset *pRecordset)
{
*adStatus = adStatusUnwantedEvent;
return S_OK;
};
STDMETHODIMP CRstEvent::raw_FetchProgress(
long Progress,
long MaxProgress,
EventStatusEnum *adStatus,
struct _Recordset *pRecordset)
{
*adStatus = adStatusUnwantedEvent;
return S_OK;
};
STDMETHODIMP CRstEvent::raw_FetchComplete(
struct Error *pError,
EventStatusEnum *adStatus,
struct _Recordset *pRecordset)
{
*adStatus = adStatusUnwantedEvent;
return S_OK;
};
//-----Implement QueryInterface, AddRef, and Release---------------------
STDMETHODIMP CRstEvent::QueryInterface(REFIID riid, void ** ppv)
{
*ppv = NULL;
if (riid == __uuidof(IUnknown) ||
riid == __uuidof(RecordsetEventsVt)) *ppv = this;
if (*ppv == NULL)
return ResultFromScode(E_NOINTERFACE);
AddRef();
return NOERROR;
}
STDMETHODIMP_(ULONG) CRstEvent::AddRef(void) { return ++m_cRef; };
STDMETHODIMP_(ULONG) CRstEvent::Release()
{
if (0 != --m_cRef) return m_cRef;
delete this;
return 0;
}
STDMETHODIMP CConnEvent::QueryInterface(REFIID riid, void ** ppv)
{
*ppv = NULL;
if (riid == __uuidof(IUnknown) ||
riid == __uuidof(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;
}
//-----Write your main block of code-------------------------------------
int main(int argc, char* argv[])
{
HRESULT hr;
DWORD dwConnEvt;
DWORD dwRstEvt;
IConnectionPointContainer *pCPC = NULL;
IConnectionPoint *pCP = NULL;
IUnknown *pUnk = NULL;
CRstEvent *pRstEvent = NULL;
CConnEvent *pConnEvent= NULL;
int rc = 0;
_RecordsetPtr pRst;
_ConnectionPtr pConn;
::CoInitialize(NULL);
hr = pConn.CreateInstance(__uuidof(Connection));
if (FAILED(hr)) return rc;
hr = pRst.CreateInstance(__uuidof(Recordset));
if (FAILED(hr)) return rc;
// Start using the Connection events
hr = pConn->QueryInterface(__uuidof(IConnectionPointContainer),
(void **)&pCPC);
if (FAILED(hr)) return rc;
hr = pCPC->FindConnectionPoint(__uuidof(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;
// Start using the Recordset events
hr = pRst->QueryInterface(__uuidof(IConnectionPointContainer),
(void **)&pCPC);
if (FAILED(hr)) return rc;
hr = pCPC->FindConnectionPoint(__uuidof(RecordsetEvents), &pCP);
pCPC->Release();
if (FAILED(hr)) return rc;
pRstEvent = new CRstEvent();
hr = pRstEvent->QueryInterface(__uuidof(IUnknown), (void **) &pUnk);
if (FAILED(hr)) return rc;
hr = pCP->Advise(pUnk, &dwRstEvt);
pCP->Release();
if (FAILED(hr)) return rc;
// Do some work
pConn->Open("dsn=Pubs;", "sa", "", adConnectUnspecified);
pRst->Open("SELECT * FROM authors", (IDispatch *) pConn,
adOpenStatic, adLockReadOnly, adCmdText);
pRst->MoveFirst();
while (pRst->EndOfFile == FALSE)
{
wprintf(L"Name = '%s'\n", (wchar_t*)
((_bstr_t) pRst->Fields->GetItem("au_lname")->Value));
pRst->MoveNext();
}
pRst->Close();
pConn->Close();
// Stop using the Connection events
hr = pConn->QueryInterface(__uuidof(IConnectionPointContainer),
(void **) &pCPC);
if (FAILED(hr)) return rc;
hr = pCPC->FindConnectionPoint(__uuidof(ConnectionEvents), &pCP);
pCPC->Release();
if (FAILED(hr)) return rc;
hr = pCP->Unadvise( dwConnEvt );
pCP->Release();
if (FAILED(hr)) return rc;
// Stop using the Recordset events
hr = pRst->QueryInterface(__uuidof(IConnectionPointContainer),
(void **) &pCPC);
if (FAILED(hr)) return rc;
hr = pCPC->FindConnectionPoint(__uuidof(RecordsetEvents), &pCP);
pCPC->Release();
if (FAILED(hr)) return rc;
hr = pCP->Unadvise( dwRstEvt );
pCP->Release();
if (FAILED(hr)) return rc;
CoUninitialize();
return 1;
}