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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

See Also

Concepts

CDaoFieldExchange Class

CDaoFieldExchange Members

Hierarchy Chart

CDaoFieldExchange::IsValidOperation

CDaoFieldExchange::m_prs

CDaoRecordset::DoFieldExchange