Hi,

how can i use discriminator with type Int32 or Enum. I get always the MappingException

My mapping:

<class name="PersistentObjects.Term, PersistentObjects" table="Terms">
<id name="Id" type="Int32" column="ID" access="field.camelcase">
<generator class="native" />
</id>
<discriminator column="Type" type="Int32"/>
<property name="Description" column="Description" type="String" />
<subclass name="PersistentObjects.Finding, PersistentObjects" discriminator-value="0"/>
<subclass name="PersistentObjects.Keyword, PersistentObjects" discriminator-value="1"/>
<subclass name="PersistentObjects.Topic, PersistentObjects" discriminator-value="2"/>
</class>

Please help
Thank you

Can you post the exception details?

NHibernate.MappingException was unhandled
Message="Could not format discriminator value 'PersistentObjects.Term' to sql string using the IType NHibernate.Type.Int32Type"
Source="NHibernate"
StackTrace:
at NHibernate.Persister.EntityPersister..ctor(PersistentClass model, ISessionFactoryImplementor factory)
at NHibernate.Persister.PersisterFactory.CreateClassPersister(PersistentClass model, ISessionFactoryImplementor factory)
at NHibernate.Impl.SessionFactoryImpl..ctor(Configuration cfg, Settings settings)
at NHibernate.Cfg.Configuration.BuildSessionFactory()
at Test.Program.Main(String[] args) in D:\PersistentObjects\Test\Program.cs:line 25

You have to specify a discriminator value for the base class (Term).

Thank you. It works. But now I want to specify enum as dicriminator type:

<class name="PersistentObjects.Term, PersistentObjects" table="Terms" discriminator-value="PersistentObjects.TermType.NoTerm">
<id name="Id" type="Int32" column="ID" access="field.camelcase">
<generator class="native" />
</id>
<discriminator column="Type" type="PersistentObjects.TermType, PersistentObjects"/>
<property name="Description" column="Description" type="String" />
<subclass name="PersistentObjects.Finding, PersistentObjects" discriminator-value="PersistentObjects.TermType.Finding"/>
</class>

where TermType is an enum:

namespace PersistentObjects
{
public enum TermType
{
NoTerm,
Finding,
}
}

I get the following exception:


NHibernate.MappingException was unhandled
Message="Illegal discriminator type: PersistentObjects.TermType"
Source="NHibernate"
StackTrace:
at NHibernate.Persister.EntityPersister..ctor(PersistentClass model, ISessionFactoryImplementor factory)
at NHibernate.Persister.PersisterFactory.CreateClassPersister(PersistentClass model, ISessionFactoryImplementor factory)
at NHibernate.Impl.SessionFactoryImpl..ctor(Configuration cfg, Settings settings)
at NHibernate.Cfg.Configuration.BuildSessionFactory()
at Test.Program.Main(String[] args) in D:\PersistentObjects\Test\Program.cs:line 25

Thank you

Why not just use Int32 for the discriminator type? The database column type is "integer".

It's a matter of taste. I find it better not to look for a meaning of e.g. 1 in a code

Just a note: looks like if the discriminator type is not specified the discriminator value for the base class can be omitted. Funny thing...

Yes, because by default the class qualified name is used as its discriminator value.

yes,i want to know who do use enum

As sergy said that u need to put the descriminator value for base class i.e Term. what value it will carry.

Like for ex. I have NodeBase base class and depending on NodeType i have created two subclasses Node (with descriminator value=0) and Leaf (with descriminator value=1) what descriminator value i expect to give for my NodeBase (which is base class) !!!!! Any non existing value like 2 or -1