I know that this is most likley a stupid question.  But in the sense of having the repository only return what is needed, why not return IEnumerable rather tan IQueryable.  I am sure it is actually because we need IQueryable for something, but unless I am wrong can't the pipes and filters and everything else be done if the repository was returning an IEnumerable.

Will delayed execution work with IEnumerable? If so - what's the gain here?

i am not sure in the gains one way or the other.  I guess that I thought I read somwhere that IEnumerable was somhow lighter or better for performance.  I am just trying to get a handle on why one would be picked over the other.  Why choose one over the other, etc. 

I was just thinking id the goal of the repository was to return the simplist collection wouldn't that be IEnumerable.  As far as deleyed execution,  I would have to say I don't know how the 2 differ.

 This is something I've thought about a lot and ultimately went with IQueryable. The main reason is to be sure I provide a rich query surface to the logic classes for people who want to customize. That said I should probably look into this more :).

Thanks...