Aggregate Root support in Entity Framework

Question

How can we tell Entity Framework about Aggregates?

1. when saving an aggregate, save entities within the aggregate
2. when deleting an aggregate, delete entitie

Answer 1

EF provides features which allows you defining your aggregates and using them:

1. This is the most painful part. EF works with entity graphs. If you have an entity like Invoice and this entity has collection of related InvoiceLine entities you can approach it like aggregate. If you are in attached scenario everything works as expected but in detached scenario (either aggregate is not loaded by EF or it is loaded by different context instance) you must attach the aggregate to context instance and tell it exactly what did you changed = set state for every entity and independent association in object graph.
2. This is handled by cascade delete - if you have related entities loaded, EF will delete them but if you don't you must have cascade delete configured on the relation in the database.
3. This is handled by concurrency tokens in the database - most commonly either timestamp or rowversion columns.
4. You must either use eager loading and load all data together at the beginning (= consistent point of view) or you will use lazy loading and in such case you will not have consistent point of view because lazy loading will load current state of relations but it will not update other parts of aggregate you have already loaded (and I consider this as performance killer if you try to implement such refreshing with EF).