You can use this event to provide user feedback or to make changes to the ConnectionString and RecordSource properties.

For example, you may implement your own version of parameterized queries by asking the user to provide some information and changing the RecordSource property accordingly.

You may also use this event to assign a System.Data.DataTable object directly to the report's Recordset property. Applications that already have the report data should do this to save time by preventing C1Report from loading its own copy of the data.

Reference

C1Report Class
C1Report Members