默认情况下，LINQ和Entity Framework加载的渴望程度如何？

Question

I'm new to LINQ and the Entity Framework. I've been fetching collections from the database using the following:

var Publications = from pubs in db.RecurringPublications
                   select pubs;

The Publications table is linked to other tables via foreign keys. I've been using this to reference properties like this:

Publications.Single().LinkedTable.LinkedTableColumn

and sometimes even further down the chain:

Publications.Single().LinkedTable.LinkedTable.LinkedLinkedTableColumn

I know you can specify lazy loading or eager loading, I was wondering how it's handled by default. Is there a maximum depth by default? Does it figure out how many joins to use at compile time?

Answer 1

It's only going to eager load what's in that specific table.

var Publications = from pubs in db.RecurringPublications
                   select pubs;

Will only get the data from your RecurringPublications table. You can specify if you want to load additional properties, but if you don't specify anything, it will only give you exactly what you ask for - nothing more.

Publications.Single().LinkedTable.LinkedTableColumn

Is lazy loading your LinkedTableColumn - now if your return is Queryable (and it is so far), it's going to do a join and return a single SQL query.

However, if the call has already been enumerated, it will make a second call.

Blog post to MSDN for info