Use the BaseDataList.DataKeyField property to specify the key field in the data source indicated by the BaseDataList.DataSource property. The specified field is used to populate the BaseDataList.DataKeys collection. This allows you to store the key field with a data listing control without displaying it in the control. The key field is commonly used in a handler for an event, such as ItemCommand or DeleteCommand, as part of an update query string to revise a specific record in the data source. The key field helps the update query string identify the appropriate record to modify.

This property cannot be set by themes or style sheet themes. For more information, see System.Web.UI.ThemeableAttribute and ASP.NET Themes Overview.