Exception: Unrecognized method call in expression

[David Campbell]

I'm attempting to get objects of one type by filtering on the id of
another. The two types have a many-to-many relationship. These are my
map files:

public TypeAMap()
{
(x => x.TypeAID).GeneratedBy.Identity();
// other mappings ...
HasManyToMany(x => x.GetTypeBs())
.Table("TypeATypeB")
.ParentKeyColumn("TypeAId")
.ChildKeyColumn("TypeBId");
}

public TypeBMap()
{
Id(x => x.TypeBId).GeneratedBy.Identity();
// other mappings ...
}

And my query:

return Session
.CreateCriteria<TypeA>()
.CreateCriteria<TypeA>(a => a.GetTypeBs())
.Add<TypeB>(b => b.TypeBId == selectedTypeBId)
.List<TypeA>();

However when I execute the query, I receive the following error:

System.Exception: Unrecognised method call in epression p.GetTypeBs
()

What am I doing wrong?

[Richard Brown (gmail)]

Hi David,

I suspect it's the call to GetTypeBs() ... this needs to be the name of the
property (association) defined in the mapping. (I'm not sure how fluentnh
determines this from the mapping example you've supplied.)

.CreateCriteria<TypeA>(a => a.GetTypeBs())

should probably be something like

.CreateCriteria<TypeA>(a => a.BsCollectionProperty)

The collection needs to be publicly exposed to use the extensions, otherwise
you'd need to use regular ICriteria for the .CreateCriteria (using strings).
(And remember you can expose it as IEnumerable is you want to make it
readonly.)

Regards,
Richard


--------------------------------------------------
From: "David Campbell" <david.d....@gmail.com>
Sent: Monday, September 14, 2009 7:23 PM
To: "NhLambdaExtensionsUsers" <nhlambdaext...@googlegroups.com>
Subject: Exception: Unrecognized method call in expression

[David D Campbell]

Thanks. That did the trick.

Stylistically, I prefer to use GetTypeBs() and AddTypeB( TypeB b) methods so that it prevents consumers from blindly setting an entirely new TypeB collection. I can appreciate using IEnumerable to prevent editing the list, but iss there a compromise between which will work yet prevent consumers from completely replacing my collection?

Thanks again.

David

[Richard Brown (gmail)]

Hi David,

 

I agree, you shouldn't expose the collection to external modification, and I too prefer methods like AddTypeB().  You can make the mutator protected, while making the accessor public.  I usually do something like:

 

class A

{

    private IList<B> _bs;

 

    public INumerable<B> Bs

    {

        get { return _bs; }

        protected set { _bs = (IList<B>)value; }           // protects the collection from being externally replaced

    }

}

 

NHibernate (and FluentNH) will happily sail past the protected methods using reflection.

 

Regards,

    Richard

[David D Campbell]

Of course. I should have thought of that. Thanks again!