Supporting Notifications
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The latest version of this topic can be found at Supporting Notifications.
Implementing Connection Point Interfaces on the Provider and Consumer
To implement notifications, a provider class must inherit from IRowsetNotifyCP and IConnectionPointContainer.
IRowsetNotifyCP implements the provider site for the connection point interface IRowsetNotify. IRowsetNotifyCP implements broadcast functions to advise listeners on the connection point IID_IRowsetNotify of changes to the contents of the rowset.
Note that you must also implement and register IRowsetNotify on the consumer (also known as the sink) using IRowsetNotifyImpl so that the consumer can handle notifications. For information about implementing the connection point interface on the consumer, see Receiving Notifications.
In addition, the class must also contain a map that defines the connection point entry, like this:
BEGIN_CONNECTION_POINT_MAP
CONNECTIONPOINT_ENTRY (IID_IRowsetNotify)
END_CONNECTION_POINT_MAP
Adding IRowsetNotify
To add IRowsetNotify, you need to add IConnectionPointContainerImpl<rowset-name> and IRowsetNotifyCP<rowset-name> to your inheritance chain.
For example, here is the inheritance chain for RUpdateRowset in UpdatePV:
Note
The sample code might differ from what is listed here; you should regard the sample code as the more up-to-date version.
///////////////////////////////////////////////////////////////////////////
// class RUpdateRowset (in rowset.h)
class RUpdateRowset :
public CRowsetImpl< RUpdateRowset, CAgentMan, CUpdateCommand,
CAtlArray< CAgentMan, CAtlArray<CAgentMan> >, CSimpleRow,
IRowsetScrollImpl< RUpdateRowset, IRowsetScroll > >,
public IRowsetUpdateImpl< RUpdateRowset, CAgentMan >,
public IConnectionPointContainerImpl<RUpdateRowset>,
public IRowsetNotifyCP<RUpdateRowset>
Setting COM Map Entries
You also need to add the following to the COM map in your rowset:
COM_INTERFACE_ENTRY
(IConnectionPointContainer)
COM_INTERFACE_ENTRY_IMPL
(IConnectionPointContainer)
These macros allow anyone calling QueryInterface for your connection point container (the basis of IRowsetNotify) to find the requested interface on your provider. For an example of how to use connection points, see the ATL POLYGON sample and tutorial.
Setting Connection Point Map Entries
You also need to add a connection point map. It should look something like:
BEGIN_CONNECTION_POINT_MAP
(rowset-name)
CONNECTION_POINT_ENTRY
(_uuidof(IRowsetNotify))
END_CONNECTION_POINT_MAP
()
This connection point map allows a component looking for the IRowsetNotify interface to find it in your provider.
Setting Properties
You also need to add the following properties to your provider. You only need to add properties based on the interfaces that you support.
| Property | Add if you support |
|---|---|
| DBPROP_IConnectionPointContainer | Always |
| DBPROP_NOTIFICATIONGRANULARITY | Always |
| DBPROP_NOTIFICATIONPHASES | Always |
| DBPROP_NOTIFYCOLUMNSET | IRowsetChange |
| DBPROP_NOTIFYROWDELETE | IRowsetChange |
| DBPROP_NOTIFYROWINSERT | IRowsetChange |
| DBPROP_NOTIFYROWSETFETCHPOSITIONCHANGE | Always |
| DBPROP_NOTIFYROWFIRSTCHANGE | IRowsetUpdate |
| DBPROP_NOTIFYROWSETRELEASE | Always |
| DBPROP_NOTIFYROWUNDOCHANGE | IRowsetUpdate |
| DBPROP_NOTIFYROWUNDODELETE | IRowsetUpdate |
| DBPROP_NOTIFYROWUNDOINSERT | IRowsetUpdate |
| DBPROP_NOTIFYROWUPDATE | IRowsetUpdate |
Most of the implementation for the notifications is already embedded in the OLE DB Provider Templates. Due to a compiler feature in Visual C++ .NET, if you do not add IRowsetNotifyCP to your inheritance chain, the compiler removes all that code from your compilation stream, thus making your code size smaller.