如何添加没有关联实体的实体，但保存关系？

Question

As far as I understand, if I change a state of an entry in context like that:

context.Entry(doc).State = EntityState.Added;

the whole object graph behind doc will be set to EntityState.Added . That is how this mechanism described here :

Note that for all of these examples if the entity being added has references to other entities that are not yet tracked then these new entities will also be added to the context and will be inserted into the database the next time that SaveChanges is called.

In my situation this behaviour is undesirable. When I receive doc entity, it's relations are already in database (were added in different context) and adding them again will cause an error. I need to add doc to a database with all references, but don't try to add other objects in graph.

Of course, I can iterate through all graph and set state explicitly, but does an easier way exist?

Answer 1

You may have a look at GraphDiff

According to this dedicated blog entry , it seems to fit your needs :

Say you have a Company which has many Contacts. A contact is not defined on its own and is a One-To-Many (with required parent) record of a Company. ie The company is the Aggregate Root. Assume you have a detached Company graph with its Contacts attached and want to reflect the state of this graph in the database.

At present using the Entity Framework you will need to perform the updates of the contacts manually, check if each contact is new and add, check if updated and edit, check if removed then delete it from the database. Once you have to do this for a few different aggregates in a large system you start to realize there must be a better, more generic way.

Well good news is that after a few refactorings I've found a nice solution to this problem.

Answer 2

In Entity Framework Core , the behavior changed, calling:

context.Entry(asset).State = EntityState.Added;

will affect only the entity and not the related ones.

👉 I know the question is for Entity Framework classic (not Core ), but surely will be more people using EF Core reaching here (like me) 😉