TCustomClientDataSet.SetOptionalParam Method

Saves a custom parameter with the data packet.

Pascal

procedure SetOptionalParam(const ParamName: string; const Value: OleVariant; IncludeInDelta: Boolean = False); virtual;

C++

virtual __fastcall SetOptionalParam(const AnsiString ParamName, const OleVariant Value, Boolean IncludeInDelta = False);

Description

You can add custom information to a data packet using the SetOptionalParam method. This information is saved with the data packet when it is saved to a file or stream, and copied with the value of the Data property. For example, by setting a parameter in the OnGetData event of provider, application servers can include custom information with the data that is sent to client applications. Call GetOptionalParam to retrieve the custom information from the data packet.

The ParamName parameter specifies the name under which the custom information is stored. It can be any value except one of the following:

UNIQUE_KEY	DEFAULT_ORDER	CHANGE_LOG	SERVER_COL
CONSTRAINTS	DATASET_CONTEXT	DATASET_DELTA	LCID
BDERECORD_X	TABLE_NAME	MD_FIELDLINKS	UPDATEMODE

The Value parameter is an OleVariant that represents the custom information.

The IncludeInDelta parameter specifies whether the parameter is also stored with the Delta property. By including the parameter in the Delta property, it is sent along with updates to the provider. The provider can then retrieve this information using the GetOptionalParam method of the client dataset passed as a parameter to an OnUpdateData event handler.

Note: Do not confuse the optional data saved by this method with the Params property.