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Problem in use if condition for nullable boolean in linq to NHibernate

Description

I have a `Person` class that `Sex` property is nullable.

public class Person { public bool? Sex {get; set;} }

And I have a query by linq to NHibernate.

var q = SessionInstance.Query<Person>(); if (dto.Sex != null) q = q.Where(p => p.Sex == dto.Sex); return q.ToList();

Now if value of dto.Sex equals `true`, result is correct.

But if value of dto.Sex equals `false` result is not correct because result is contain persons that Sex is false or null.

I checked profiler for this query:

select * from Person_Person person0_ where case when person0_.Sex = 1 then 1 else 0 end = case when 0 /* @p0 */ = 1 then 1 else 0 end

I don't know why that LINQ query generates a case statement, that's really weird.

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Alex Zaytsev 
October 31, 2016 at 8:41 PM

Alex Zaytsev 
June 8, 2016 at 12:13 AM

In EF they do very-deep null propagation analysis on expression and extend it to conditional/more complex expression. This is not a matter of just adding random case statements to the query. I'll nominate this to 5.0

Oskar Berggren 
September 2, 2014 at 8:44 PM

Changing back to 4.1.0. Fixing this involves changing the result of a previously non-failing query, so it could mean a breaking change for some application, right?

Oskar Berggren 
December 13, 2012 at 10:43 PM

Let's see if we can get this done in NH4.0.

Oskar Berggren 
December 13, 2012 at 10:42 PM
(edited)

This might be relevant to explore in relation to this issue or something similar for other nullable primitives:

With Employee.ReportsTo as Nullable<int>, and this LINQ: var queryable = session.Query<Employee>() .Where(e => (e.ReportsTo != e.ReportsTo) == null);

L2EF generates:

WHERE CASE WHEN ( [Extent1].[flags] = [Extent1].[flags] ) THEN Cast(1 AS BIT) WHEN ( [Extent1].[flags] <> [Extent1].[flags] ) THEN Cast(0 AS BIT) END IS NULL

Nhibernate 3.3.x currently generates

where case when employee0_.ReportsTo<>employee0_.ReportsTo then 1 else 0 end=@p0; @p0 = NULL [Type: Boolean (0)]

And these two queries will of course give different results.

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Created March 26, 2012 at 10:37 AM
Updated December 18, 2017 at 9:26 PM
Resolved February 14, 2017 at 11:33 PM
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