CDaoFieldExchange::m_nOperation
Identifies the operation to be performed on the CDaoRecordset object associated with the field exchange object.
Remarks
The CDaoFieldExchange object supplies the context for a number of different DFX operations on the recordset.
注意
The PSEUDO NULL value described under the MarkForAddNew and SetFieldNull operations below is a value used to mark fields Null. The DAO record field exchange mechanism (DFX) uses this value to determine which fields have been explicitly marked Null. PSEUDO NULL is not required for COleDateTime and COleCurrency fields.
Possible values of m_nOperation are:
Operation |
Description |
|---|---|
AddToParameterList |
Builds the PARAMETERS clause of the SQL statement. |
AddToSelectList |
Builds the SELECT clause of the SQL statement. |
BindField |
Binds a field in the database to a memory location in your application. |
BindParam |
Sets parameter values for the recordset's query. |
Fixup |
Sets the Null status for a field. |
AllocCache |
Allocates the cache used to check for "dirty" fields in the recordset. |
StoreField |
Saves the current record to the cache. |
LoadField |
Restores the cached data member variables in the recordset. |
FreeCache |
Frees the cache used to check for "dirty" fields in the recordset. |
SetFieldNull |
Sets a field's status to Null and value to PSEUDO NULL. |
MarkForAddNew |
Marks fields "dirty" if not PSEUDO NULL. |
MarkForEdit |
Marks fields "dirty" if they do not match the cache. |
SetDirtyField |
Sets field values marked as "dirty." |
DumpField |
Dumps a field's contents (debug only). |
MaxDFXOperation |
Used for input checking. |
Requirements
Header: afxdao.h