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Consumer Wizard-Generated Methods 

The ATL OLE DB Consumer Wizard and the MFC Application Wizard generate certain functions of which you should be aware. Note that some methods are implemented differently in attributed projects, so there are a few caveats; each case is covered below. For information about viewing injected code, see Debugging Injected Code.

  • OpenAll opens the data source, rowsets, and turns on bookmarks if they are available.

  • CloseAll closes all open rowsets and releases all command executions.

  • OpenRowset is called by OpenAll to open the consumer's rowset or rowsets.

  • GetRowsetProperties retrieves a pointer to the rowset's property set with which properties can be set.

  • OpenDataSource opens the data source using the initialization string you specified in the Data Link Properties dialog box.

  • CloseDataSource closes the data source in an appropriate manner.

OpenAll and CloseAll

HRESULT OpenAll(); 
void CloseAll();

The following example shows how you can call OpenAll and CloseAll when you execute the same command repeatedly. Compare the code example in CCommand::Close, which shows a variation that calls Close and ReleaseCommand instead of CloseAll.

int main(int argc, char* argv[])
{
   HRESULT hr;

   hr = CoInitialize(NULL);

   CCustOrdersDetail rs;      // Your CCommand-derived class
   rs.m_OrderID = 10248;      // Open order 10248
   hr = rs.OpenAll();         // (Open also executes the command)
   hr = rs.MoveFirst();         // Move to the first row and print it
   printf( "Name: %s, Unit Price: %d, Quantity: %d, Discount %d, Extended Price %d\n", rs.m_ProductName, rs.m_UnitPrice.int64, rs.m_Quantity, rs.m_Discount, rs.m_ExtendedPrice.int64 );

   // Close the first command execution
   rs.Close();


   rs.m_OrderID = 10249;      // Open order 10249 (a new order)
   hr = rs.Open();            // (Open also executes the command)
   hr = rs.MoveFirst();         // Move to the first row and print it
   printf( "Name: %s, Unit Price: %d, Quantity: %d, Discount %d, Extended Price %d\n", rs.m_ProductName, rs.m_UnitPrice.int64, rs.m_Quantity, rs.m_Discount, rs.m_ExtendedPrice.int64 );

   // Close the second command execution;
   // Instead of rs.CloseAll() you could call
   // rs.Close() and rs.ReleaseCommand():
   rs.CloseAll();

   CoUninitialize();
   return 0;
}

Remarks

Note that if you define a HasBookmark method, the OpenAll code sets the DBPROP_IRowsetLocate property; make sure you only do this if your provider supports that property.

OpenRowset

// OLE DB Template version: 
HRESULT OpenRowset(DBPROPSET* pPropSet = NULL)
// Attribute-injected version:
HRESULT OpenRowset(const CSession& session, LPCWSTR szCommand = NULL);

OpenAll calls this method to open the rowset or rowsets in the consumer. Typically, you do not need to call OpenRowset unless you want to work with multiple data sources/sessions/rowsets. OpenRowset is declared in the command or table class header file:

// OLE DB Template version:
HRESULT OpenRowset(DBPROPSET *pPropSet = NULL)
{
   HRESULT hr = Open(m_session, NULL, pPropSet);
   #ifdef _DEBUG
   if(FAILED(hr))
      AtlTraceErrorRecords(hr);
   #endif
   return hr;
}

The attributes implement this method differently. This version takes a session object and a command string that defaults to the command string specified in db_command, although you can pass a different one. Note that if you define a HasBookmark method, the OpenRowset code sets the DBPROP_IRowsetLocate property; make sure you only do this if your provider supports that property.

// Attribute-injected version:
HRESULT OpenRowset(const CSession& session, LPCWSTR szCommand=NULL)
{

   DBPROPSET *pPropSet = NULL;
   CDBPropSet propset(DBPROPSET_ROWSET);
   __if_exists(HasBookmark)

   {
      propset.AddProperty(DBPROP_IRowsetLocate, true);
      pPropSet= &propset;
      }
...
}

GetRowsetProperties

void GetRowsetProperties(CDBPropSet* pPropSet);

This method retrieves a pointer to the rowset's property set; you can use this pointer to set properties such as DBPROP_IRowsetChange. GetRowsetProperties is used in the user record class as follows. You can modify this code to set additional rowset properties:

void GetRowsetProperties(CDBPropSet* pPropSet)
{
   pPropSet->AddProperty(DBPROP_CANFETCHBACKWARDS, true, DBPROPOPTIONS_OPTIONAL);
   pPropSet->AddProperty(DBPROP_CANSCROLLBACKWARDS, true, DBPROPOPTIONS_OPTIONAL);
   pPropSet->AddProperty(DBPROP_IRowsetChange, true, DBPROPOPTIONS_OPTIONAL);
   pPropSet->AddProperty(DBPROP_UPDATABILITY, DBPROPVAL_UP_CHANGE | DBPROPVAL_UP_INSERT | DBPROPVAL_UP_DELETE);
}

Remarks

You should not define a global GetRowsetProperties method because it could conflict with the one defined by the wizard. Note that this is a wizard-generated method that you get with templated and attributed projects; the attributes do not inject this code.

OpenDataSource and CloseDataSource

HRESULT OpenDataSource(); 
void CloseDataSource();

Remarks

The wizard defines the methods OpenDataSource and CloseDataSource; OpenDataSource calls CDataSource::OpenFromInitializationString.

See Also

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