The solution is simple. *Use primary key (Id)* to compare to null: s.ClassC.
*Id* == null
Then you'll get:
select
classa0_.Id as col_0_0_,
(select
cast(count(*) as INT)
from
[ClassB] classb1_
where
classb1_.Id is null) as col_1_0_
from
[ClassA] classa0_
The reason is that NHibernate is smart enough to recognize primary key of
an entity and skips fetching related table. I comes handy when you would
create more complex queries.
It definitely solves the problem for the simplified example, you've shared,
but what about the real-life use case? Let me know if it helps :)
On Thursday, August 20, 2015 at 10:50:55 AM UTC+2, Иван Иванов wrote:
>
> Hello.
>
> public class ClassA : IEntity
> {
> public virtual int Id { get; set; }
>
> public virtual string Name { get; set; }
> }
>
> public class ClassB : IEntity
> {
> public virtual int Id { get; set; }
>
> public virtual string Name { get; set; }
>
> public virtual ClassC ClassC { get; set; }
> }
>
> public class ClassC : IEntity
> {
> public virtual string Name { get; set; }
>
> public virtual int Id { get; set; }
> }
>
> Query:
> var list = session
> .Query<ClassA>()
> .Select(x => new
> {
> x.Id,
> Count = session.Query<ClassB>().Count(s =>
> s.ClassC == null)
> })
> .ToList();
>
> Result:
>
> select classa0_.CLASS_A_ID as col_0_0_,
> (select cast(count(*) as INT)
> from CLASS_B classb1_,
> CLASS_C classc2_
> where classb1_.CLASS_C_ID = classc2_.CLASS_C_ID
> and (classb1_.CLASS_C_ID is null)) as col_1_0_
> from CLASS_A classa0_
>
>
>
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