The Inserting event is raised before a new object is persisted to the data source. The Inserting event enables you to modify or verify the object being added, add a different object, or cancel the operation. You can access the object to be added from the Entity property of the EntityDataSourceChangingEventArgs object. If supplying a different object, the user is responsible for setting the correct entity type in the Entity property.
When you handle the exception in the Inserting event handler, set the ExceptionHandled property to true. This prevents the exception from being raised again. When you specify a value of false for the ExceptionHandled property, the EntityDataSource re-raises the exception.