MDAC 2.5 SDK - OLE DB Programmer's Reference
OLE DB Interfaces

IRowsetNotify::OnFieldChange

Notifies the consumer of any change to the value of a column.

HRESULT OnFieldChange (
   IRowset *      pRowset,
   HROW           hRow,
   ULONG          cColumns,
   ULONG          rgColumns[],
   DBREASON       eReason,
   DBEVENTPHASE   ePhase,
   BOOL           fCantDeny);

Parameters

pRowset

[in]
A pointer to the rowset, because the consumer may be receiving notifications from multiple rowsets and this identifies which one is calling.

hRow

[in]
The handle of the row in which the column value was changed. After this method returns, the reference count of this row will be unchanged unless the consumer explicitly changes it. This is different from other methods that return rows to the consumer, in which the provider explicitly increments the reference count. Therefore, if the consumer wants to guarantee that this row handle is valid after this method returns, it must call IRowset::AddRefRows for the row while it is processing this method.

cColumns

[in]
The count of columns in rgColumns.

rgColumns

[in]
An array of columns in the row for which the value was changed.

eReason

[in]
The reason of the event that caused this change. If this value is not recognized by the method, the method returns S_OK or DB_S_UNWANTEDREASON.

ePhase

[in]
The phase of this notification.

fCantDeny

[in]
When this flag is set to TRUE, the consumer cannot veto the event by returning S_FALSE because the provider cannot undo the event.

Return Code

S_OK

The method succeeded.

S_FALSE

The event/phase is vetoed by reason of logical objection or a failure to be able to implement.

DB_S_UNWANTEDPHASE

The consumer is not interested in receiving this phase for this reason. The provider can optimize by making no further calls with this reason and phase. The phases for other reasons are unaffected.

DB_S_UNWANTEDREASON

The consumer is not interested in receiving any phases for this reason. The provider can optimize by making no further calls with this reason.

E_FAIL

A consumer-specific error occurred. The provider continues the operation.

Comments

Possible reasons are DBREASON_COLUMN_SET and DBREASON_COLUMN_RECALCULATED.

All phases can occur for a DBREASON_COLUMN_SET event. The new value is visible beginning with the DBEVENTPHASE_SYNCHAFTER phase. For a DBREASON_COLUMN_RECALCULATED event, only the DBEVENTPHASE_DIDEVENT phase occurs.

Providers call IRowsetNotify::OnFieldChange once for all of the columns set in a single call to IRowsetChange::SetData, and once for all of the changes to calculated columns of a row based on an update to that row. Setting a column to its current value can, but is not required to, generate a notification for that column.

Unless the consumer returns S_FALSE, the provider continues the operation. This is true even if the consumer returns E_FAIL or any other error code.