Assembly: System.Web (in system.web.dll)
By adding an event handler delegate to handle the Selecting event, you can perform any additional preprocessing required or cancel the database query entirely. Because the SqlDataSourceSelectingEventArgs class is derived from the SqlDataSourceCommandEventArgs class, you can cancel a pending SqlDataSource database query by setting the Cancel property to true. You can examine and manipulate the CommandText, Parameters collection, and other database query properties prior to running the query by accessing the DbCommand object exposed by the Command property. You can also examine the DataSourceSelectArguments object that is passed to the Select method by accessing the Arguments property.
The SqlDataSourceSelectingEventArgs class is used in the OnSelecting method to provide access to a SqlDataSource database query before it is run.
The SqlDataSource control exposes many events that you can handle to work with the underlying data objects during the course of a data operation. The following table lists the events and associated EventArgs classes and event handler delegates.
Occurs before the data is retrieved.
Occur before an insert, update, or delete operation is performed.
Occur after the data retrieval, insert, update, or delete operation completes.