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Make a ThenFetch for the QueryOver provider/syntax

Description

The LINQ provider has a ThenFetch method to eagerly load a table referenced by another table referenced by another table (so with A.B.C, B can be eagerly loaded through Fetch, C can be eagerly loaded through ThenFetch). The QueryOver provider doesn't have anything similar (at least if B is a "collection". Haven't tested with B being 0-1). You can go around the problem using something like:

B aliasB = null;
C aliasC = null;

query = query.JoinAlias(p => p.B, () => aliasB, JoinType.LeftOuterJoin)
.JoinAlias(() => B.C, () => aliasC, JoinType.LeftOuterJoin);

but the syntax is more complex and I'm not even sure it's equivalent (taken from http://stackoverflow.com/questions/4801235/nhibernate-3-alternatives-to-thenfetch-in-queryover )

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Massimiliano Alberti December 20, 2011 at 4:15 PM

Yes perfectly... I didn't know. I thought that writing something like that would make everything go boom if B was empty for some B, but clearly it doesn't because the expression is parsed, not executed. Thanks a lot!

Richard Brown December 20, 2011 at 2:48 PM

https://github.com/nhibernate/nhibernate-core/blob/master/src/NHibernate.Test/Criteria/Lambda/QueryOverFixture.cs#L732

There is already syntax available for collection properties:

query
.Fetch(p => p.B)
.Fetch(p => p.B.C) // if B is not a collection ... or
.Fetch(p => p.B[0].C) // if B is a collection ... or
.Fetch(p => p.B.First().C) // if B is an IEnumerable (using .First() extension method)

Does that provide the functionality you were after?

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Created December 9, 2011 at 4:47 PM
Updated December 20, 2011 at 8:02 PM
Resolved December 20, 2011 at 8:02 PM
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