Transfers double float data between the field data members of a CDaoRecordset object and the columns of a record on the data source.
void AFXAPI DFX_Double( CDaoFieldExchange* pFX, LPCTSTR szName, double& value, DWORD dwBindOptions = AFX_DAO_ENABLE_FIELD_CACHE );
- A pointer to an object of class CDaoFieldExchange. This object contains information to define the context for each call of the function. For more information about the operations a CDaoFieldExchange object can specify, see the article DAO Record Field Exchange: How DFX Works.
- The name of a data column.
- The value stored in the indicated data member — the value to be transferred. For a transfer from recordset to data source, the value, of type double, is taken from the specified data member. For a transfer from data source to recordset, the value is stored in the specified data member.
- An option that lets you take advantage of MFC's double buffering mechanism for detecting recordset fields that have changed. The default, AFX_DAO_ENABLE_FIELD_CACHE, uses double buffering. The other possible value is AFX_DAO_DISABLE_FIELD_CACHE. If you specify this value, MFC does no checking on this field. You must call SetFieldDirty and SetFieldNull yourself.
These options are explained further in the article DAO Recordset: Binding Records Dynamically.
Note You can control whether data is double buffered by default by setting CDaoRecordset::m_bCheckCacheForDirtyFields.
Data is mapped between type DAO_R8 in DAO and type double float in the recordset.