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(Tenant)))),
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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