In hopes that I can get a solution to my problem, I did some more
research with the NHibernate codebase. The problem seems to be in
SingleTableEntityPersister.cs, line 543, DiscriminatorFilterFragment
(string alias) method which has this code:
string[] subclasses = SubclassClosure;
for (int i = 0; i < subclasses.Length; i++)
{
IQueryable queryable = (IQueryable)
Factory.GetEntityPersister(subclasses[i]);
if (!queryable.IsAbstract)
frag.AddValue(queryable.DiscriminatorSQLValue);
}
StringBuilder buf = new
StringBuilder(50).Append(" and ").Append
(frag.ToFragmentString().ToString());
When trying to create the discriminator filter fragment ("IN (2, 3,
4)") for IActivity, the system only sees "Activity" as the subclass
(result of SubclassClosure). Which is fine; I'd expect that if it
recursively added all discriminator values not only for subclasses but
for subclasses of subclasses.
Also, when I take the interface out of it, it seems to be ok with
inheritance at multiple levels. The problem only occurs when I try to
make an interface the base type.
Finally, I saw that I made a mistake in my example here; Activity
should have been coded as abstract but wasn't. The problem still
remains when I make this correction.
Is there something I need to do to provide more information beyond
this?
On Jun 25, 1:36 pm, Michael Hedgpeth <[email protected]> wrote:
> I have an issue with NHibernate giving me the following error:
>
> System.NotSupportedException: Attempting to parse a null value into an
> sql string (column:activity0_.Type).
> at NHibernate.SqlCommand.InFragment.ToFragmentString() in
> InFragment.cs: line 109
> at
> NHibernate.Persister.Entity.SingleTableEntityPersister.DiscriminatorFilterFragment
> (String alias) in SingleTableEntityPersister.cs: line 551
>
> I set up a simple solution to reproduce the error. I have the
> following domain classes:
>
> public interface IActivity
> {
> Guid Id { get; set; }
> }
>
> public class Activity : IActivity
> {
> public DateTime StartTime { get; set; }
> public Guid Id { get; set; }
> }
>
> public class Running : Activity
> {
> public string Where { get; set; }
> }
>
> public class Talking : Activity
> {
> public string ToWhom { get; set; }
> }
>
> And the following mapping xml:
>
> <?xml version="1.0" ?>
> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
> assembly="NHibernateTesting"
> namespace="NHibernateTesting" >
> <class name="IActivity"
> lazy="false"
> table="Activity"
> discriminator-value="0"
> abstract="true">
> <id name="Id">
> <generator class="guid" />
> </id>
> <discriminator column="Type" type="Int16" />
> <subclass name="Activity"
> discriminator-value="1"
> abstract="true"
> lazy="false">
> <property name="StartTime" />
> </subclass>
> <subclass name="Running"
> discriminator-value="2"
> lazy="false"
> extends="Activity">
> <property name="Where" />
> </subclass>
> <subclass name="Talking"
> discriminator-value="3"
> lazy="false"
> extends="Activity">
> <property name="ToWhom" />
> </subclass>
> </class>
> </hibernate-mapping>
>
> Any idea what I am doing wrong?
>
> Thanks!
> Michael Hedgpeth
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