ADO Event Model and Asynchronous Operations

The ADO Event Model supports certain synchronous and asynchronous ADO operations that issue events before the operation starts or after it completes. An event is actually a call to an event handler routine.

Event handlers that are called before the operation starts allow you to examine or modify the operation parameters, then either cancel the operation or allow it to complete.

Event handlers that are called after an operation completes are especially important now that ADO 2.0 supports asynchronous operations. For example, an application that starts an asynchronous Recordset.Open operation is notified by an execution complete event when the operation concludes.

There are two families of events:

• ConnectionEvents—Events are issued when a transaction on a connection begins, is committed, or is rolled back; when a Command executes; and when a Connection starts or ends.
  
  
• RecordsetEvents—Events are issued when you navigate through the rows of a Recordset object; change a field in a row of a Recordset; change a row in a Recordset; or make any change whatsoever in the Recordset.