Thanks Richard for your response. If the NH dev team recommendation
is to use linq to cast the object array to the intended object type, I
feel this is a unacceptable and sloppy solution. Having the API
return an object array, when it *knows* the type of object makes me
feel like I'm using an API from 2003. Then having to box each
property and map them manually is tedious and error prone. I guess I
fail to see why queries with the QueryOver api and projections
wouldn't use the same method that NH uses to populate full objects.
If this is the intended behavior, then I consider this a bug, even if
it is a non-functional bug.
Also, I did try to use a ResultTransformer, but was unsuccessful:
Session.QueryOver<Tenant>()
.Select(x => x.Id, x => x.FirstName, x
=> x.LastName)
.UnderlyingCriteria.SetResultTransformer(Transformers.AliasToBean(typeof(Tenant)))
.List<Tenant>()
Is there a better way of doing this so that it works?
Thanks,
Jim
On May 8, 3:44 am, "Richard Brown \(gmail\)" <[email protected]>
wrote:
> Hi Jim,
>
> QueryOver returns an object[] in this case (like ICriteria which it is built
> on). I think your options are to use a ResultTransformer (which looking at
> it is missing from the IQueryOver interface, but can be added to the
> UnderlyingCriteria), or use an extension method from the LINQ namespace:
>
> var tenants =
> Session.QueryOver<Tenant>()
> .Select(
> x => x.Id,
> x => x.FirstName,
> x => x.LastName)
> .List<object[]>()
> .Select(properties => new Tenant() {
> Id = (int)properties[0],
> FirstName = (string)properties[1],
> LastName = (string)properties[2],
> });
>
> Richard
>
> --------------------------------------------------
> From: "Jim Geurts" <[email protected]>
> Sent: Friday, May 07, 2010 5:43 PM
> To: "nhusers" <[email protected]>
> Subject: [nhusers] Error using projections and a result collection
>
>
>
>
>
> > Hi all,
>
> > I'm trying to use projections to only return a few properties of my
> > domain object from the db. The code I'm using looks like:
>
> > var tenants = Session.QueryOver<Tenant>()
> > .Select(x => x.Id, x => x.FirstName, x => x.LastName)
> > .List<Tenant>();
>
> > The generated sql is spot on, but unfortunately, things are not
> > working when NHibernate tries to map the result to an
> > IEnumerable<Tenant>. It throws an exception similar to:
>
> > The value "System.Object[]" is not of type "MyDomain.Tenant" and
> > cannot be used in this generic collection.
> > Parameter name: value
> > System.ThrowHelper.ThrowWrongValueTypeArgumentException(Object value,
> > Type targetType) +122
>
> > System.Collections.Generic.List`1.System.Collections.IList.Add(Object
> > item) +150
> > NHibernate.Util.ArrayHelper.AddAll(IList to, IList from) in d:
> > \Builds\NHibernate\nhibernate\src\NHibernate\Util\ArrayHelper.cs:201
> > NHibernate.Impl.SessionImpl.List(CriteriaImpl criteria, IList
> > results) in d:\Builds\NHibernate\nhibernate\src\NHibernate\Impl
> > \SessionImpl.cs:1994
>
> > I've tried to set a transformer
> > (using
> > .UnderlyingCriteria.SetResultTransformer(Transformers.AliasToBean(typeof(Te
> > nant)))),
> > but it did not seem to help. This is using NHibernate 3.0.0.1001
>
> > Any ideas what is going on and how to fix it?
>
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