Is there any work-around for NHibernate-to-LINQ not supporting subqueries?

Question

I know LINQ-to-NHibernate currently does not support sub-queries (http://ayende.com/Blog/archive/2009/07/26/nhibernate-linq-1.0-released.aspx).

Is there any workaround about it?

score 3 · Accepted Answer · edited May 23 '17 at 10:32

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linq-to-nh DOES support sub queries in where clause. It is exact thing I needed. I was wrong with my previous answer. Both martijnboland and Stefan Steinegger were right. To see how you do sub-queries in linq-to-nh see this and this. There is also limitations.

edited May 23 '17 at 10:32

Community

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answered Nov 15 '10 at 18:25

Afshar Mohebi

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score 1 · Answer 2 · answered Mar 02 '10 at 09:32

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I think the workaround is simply to use HQL or Criteria.

answered Mar 02 '10 at 09:32

Stefan Steinegger

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Unfortunately Criteria does not support subqueries too. Indeed LINQ-to-NHibernate is based on ICriteria and this disability origins from ICriteria itself. – Afshar Mohebi Mar 02 '10 at 09:39
Criteria **DOES** support subqueries. It's built with `DetachedCriteria` and added with `.Add(Subqueries.Blah(subquery))` (where `Blah` is `Exists` or `PropertyIn` or something like this) – Stefan Steinegger Mar 03 '10 at 16:16
after a long long time I'm convinced that you were right. Sorry! – Afshar Mohebi Nov 15 '10 at 18:27

score 0 · Answer 3 · answered Mar 02 '10 at 09:24

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I have not worked with nhibernate to linq but i'm sure that you can translate almost any subquery to a join

answered Mar 02 '10 at 09:24

Drevak

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Unfortunately it does not support joins too! – Afshar Mohebi Mar 02 '10 at 09:27
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Note that there is a difference between subqueries in the select and subqueries in the where clause: subqueries in the where clause are supported and work fine (Any(), Count() etc.) – martijnboland Mar 02 '10 at 09:35
Dear martijn, I'm going to use "select subqueries" – Afshar Mohebi Mar 02 '10 at 09:37
@martijn, After a long long time I realized that the sub-query that I needed was sub query in `where` clause. You were right. – Afshar Mohebi Nov 15 '10 at 18:28

score 0 · Answer 4 · answered Mar 03 '10 at 15:10

I have used a two part LINQ query as a work around. A LINQ-to-NHibernate for not related sub query section and a LINQ-to-Object for sub query related section of the query. Please see http://afsharm.blogspot.com/2010/03/dealing-with-subqueries-in-linq-to.html for more detail.

Is there any work-around for NHibernate-to-LINQ not supporting subqueries?

4 Answers4