Question

So I’ve been advised a few times to disable lazy loading when building an application with the above frameworks, and that ToList() will force the queries in my repository to execute. I was told that I would avoid certain “traps” I might run into if I used AsEnumerable().

On a recent question, however, I included a bunch of ToList()s in my code examples, and startled a number of people that assured me IEnumerable is much better to return.

I’m thoroughly confused now, to say the least.

Should I be returning IEnumerable in my repository, then converting them to List in my view models? Should I use ToList() straightaway in my repository like I was before? Was I suppose to leave deferred execution enabled in the first place?

Jiminy Christmas…

Edit:
So, being that I disabled lazy loading, based on earlier advice, should I then re-enable it, return IEnumerable / IQueryable from my repository, and convert the collection to a List in my view models, if needed?

One of the answers below associates IEnumerable with eager execution, while I was under the impression that only ToList() would force immediate execution of the query.

I stumbled across this, this, and this that all contain some interesting discussion related to this question.

Answer 1

Call ToList(), returning an IEnumerable in your repository, if:

1. You want to control the output set provided to the consumer (i.e. you don’t want them to run queries on it), and
2. You don’t mind eager execution.

Return IQueryable, or IEnumerable via AsEnumerable(), in your repository if:

1. You don’t mind your consumers running queries on the output set, and
2. You want deferred execution.

See Also
http://thinkbeforecoding.com/post/2009/01/19/Repositories-and-IQueryable-the-paging-case