CODEWITHSUNDEEP
c#linqnhibernatelinq-to-nhibernate
Remco Ros
Remco Ros

Reputation: 1477

NHibernate Linq and DistinctRootEntity

When I execute the following query, I get an exception telling me that 'feedItemQuery' contains multiple items (so SingleOrDefault doesn't work).

This is expected behaviour when using the Criteria api WITHOUT the DistinctRootEntity transformer, but when using linq, I expect to get a single root entity (FeedItem, with the property Ads (of ICollection) containing all Ads).

Is there a way to tell NHibernate.Linq to use the DistinctRootEntity transformer?

My query:

var feedItemQuery = from ad in session.Linq<FeedItem>().Expand("Ads")
                   where ad.Id == Id
                   select ad;

var feedItem = feedItemQuery.SingleOrDefault(); // This fails !?

The mapping:

<class name="FeedItem" table="FeedItems" proxy="IFeedItem">
    <id name="Id" type="Guid">
        <generator class="guid.comb"></generator>
    </id>
 ...
    <set name="Ads" table="Ads">
        <key column="FeedItemId" />
        <one-to-many class="Ad" />
    </set>
</class>

Thanks in advance

Upvotes: 4

Views: 2837

Answers (2)

Simon
Simon

Reputation: 5493

You can use the RegisterCustomAction method to set the result transformer:

var linqsession = session.Linq<FeedItem>();
linqsession.QueryOptions.RegisterCustomAction(c => c.SetResultTransformer(new DistinctRootEntityResultTransformer()));
var feedItemQuery = from ad in linqsession.Expand("Ads")
                    where ad.Id == Id
                    select ad

Upvotes: 6

Missy Hwe Lee
Missy Hwe Lee

Reputation:

var feedItemQuery = from ad in session.Linq().Expand("Ads")
where ad.Id == Id
select ad**.FirstOrDefault();**

Upvotes: 0

Related Questions