Client-side life cycle

Client-side query life cycle events on the EntityManager include Querying, Fetching, and Queried. These are summarized in the table below.

DevForce raises the client-side Querying event as query execution begins. The Fetching event is raised before sending the query to the EntityServer; if a query can be satisfied from cache, then Fetching is not raised. The Queried event is raised just before returning query results. We can listen to these events by attaching a custom handler.

Both the Querying and the Fetching events provide the query object. Your handler can examine the object (it implements IEntityQuery and choose to let the query continue as is, continue after modification, or cancel it. If you cancel the query, the Entity Manager method returns as if it found nothing. If the method returns a scalar entity, it yields the return entity type’s Null Entity; otherwise, it returns a null entity list. Beware of canceling an entity navigation list query method.

The Queried event fires just before the query method returns. Entities have been fetched and merged into the cache. The event arguments include a list, EntitiesChanged, of any entities added to or modified in the cache. Note that this list could include entities of the target entity type – the kind we expected returned from the query – but also of other types brought in via Includes or by virtue of query inversion.

Client-Side Life-Cycle Events

Corresponding to each of these events is a protected virtual method on the EntityManager that can be used to perform the same task directly in a subclassed EntityManager.

EntityQueryingEventArgs

EntityFetchingEventArgs

EntityQueriedEventArgs

Note that this is the non-generic version of the EntityQueriedEventArgs<T> class. As a result the Query and Results properties here are non-generic as well. i.e. IEntityQuery vs IEntityQuery<T>, IEnumerable vs IEnumerable<T>.