Fluent Nhibernate HasMany

Question

I am having a gap in understanding and I would appreciate any help.

When I create a HasMany relationship using a list, nhibernate creates an "index" column on my child table. If I query the table using a join, it crashes with "Null Index on collection"

What I am not understanding is -- how is this "index" column managed/populated?

My pertinent code:

Parent (Product)

  Class:
       public class License
       {
             ...
             public virtual IList<License>  Licenses { get; set; }
             public Product()
             {
                Licenses = (IList<License>)new List<License>();
             }
       }

   Mapping:

    HasMany<License>(x => x.Licenses)
        .Inverse()
        .Not.LazyLoad()
        .AsList()
        .Cascade.AllDeleteOrphan()
        .ForeignKeyCascadeOnDelete()
        .KeyNullable()
        .KeyColumn("Product_ID")

Child (License):

  Class:
       public class License
       {
             ...
             public virtual Product_ID {get; set;}
       }

  Mapping: 


    ...
    References<Product>(x => x.Product_ID)
        .Column("ParentProduct");
    ...

And my join:

   criteria.Add(Restrictions.Disjunction()
                        .Add(Restrictions.Like("Name", kw))
                        .Add(Restrictions.Like("Description", kw)))
                        .CreateAlias("Licenses", "License",   NHibernate.SqlCommand.JoinType.LeftOuterJoin);

I end up with:

[HibernateException: null index column for collection: Test.Licenses]
   NHibernate.Persister.Collection.AbstractCollectionPersister.ReadIndex(IDataReader rs, String[] aliases, ISessionImplementor session) in D:\source\elysium\Elysium.Web\FNH\src\NHibernate\Persister\Collection\AbstractCollectionPersister.cs:703
   NHibernate.Collection.PersistentList.ReadFrom(IDataReader rs, ICollectionPersister role, ICollectionAliases descriptor, Object owner) in D:\source\elysium\Elysium.Web\FNH\src\NHibernate\Collection\PersistentList.cs:120
   NHibernate.Loader.Loader.ReadCollectionElement(Object optionalOwner, Object optionalKey, ICollectionPersister persister, ICollectionAliases descriptor, IDataReader rs, ISessionImplementor session) in D:\source\elysium\Elysium.Web\FNH\src\NHibernate\Loader\Loader.cs:706
   NHibernate.Loader.Loader.ReadCollectionElements(Object[] row, IDataReader resultSet, ISessionImplementor session) in D:\source\elysium\Elysium.Web\FNH\src\NHibernate\Loader\Loader.cs:385
   NHibernate.Loader.Loader.GetRowFromResultSet(IDataReader resultSet, ISessionImplementor session, QueryParameters queryParameters, LockMode[] lockModeArray, EntityKey optionalObjectKey, IList hydratedObjects, EntityKey[] keys, Boolean returnProxies) in D:\source\elysium\Elysium.Web\FNH\src\NHibernate\Loader\Loader.cs:326
   NHibernate.Loader.Loader.DoQuery(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies) in D:\source\elysium\Elysium.Web\FNH\src\NHibernate\Loader\Loader.cs:453
   NHibernate.Loader.Loader.DoQueryAndInitializeNonLazyCollections(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies) in D:\source\elysium\Elysium.Web\FNH\src\NHibernate\Loader\Loader.cs:236
   NHibernate.Loader.Loader.DoList(ISessionImplementor session, QueryParameters queryParameters) in D:\source\elysium\Elysium.Web\FNH\src\NHibernate\Loader\Loader.cs:1649
   NHibernate.Loader.Loader.ListIgnoreQueryCache(ISessionImplementor session, QueryParameters queryParameters) in D:\source\elysium\Elysium.Web\FNH\src\NHibernate\Loader\Loader.cs:1568
...

EDIT

I changed the collection to Bag (or Set) and I get a different issue:

Line 30:        public void SetPropertyValues(object target, object[] values)
Line 31:        {
Line 32:            setDelegate(target, values, setterCallback);
Line 33:        }
Line 34: 


Source File: D:\source\Test\FNH\src\NHibernate\Bytecode\Lightweight\AccessOptimizer.cs    Line: 32

Stack Trace:

[InvalidCastException: Specified cast is not valid.]
   (Object , Object[] , SetterCallback ) +409
   NHibernate.Bytecode.Lightweight.AccessOptimizer.SetPropertyValues(Object target, Object[] values) in D:\source\Test\FNH\src\NHibernate\Bytecode\Lightweight\AccessOptimizer.cs:32
   NHibernate.Tuple.Entity.PocoEntityTuplizer.SetPropertyValuesWithOptimizer(Object entity, Object[] values) in D:\source\Test\FNH\src\NHibernate\Tuple\Entity\PocoEntityTuplizer.cs:292

[PropertyAccessException: Invalid Cast (check your mapping for property type mismatches); setter of Test.License]
   NHibernate.Tuple.Entity.PocoEntityTuplizer.SetPropertyValuesWithOptimizer(Object entity, Object[] values) in D:\source\Test\FNH\src\NHibernate\Tuple\Entity\PocoEntityTuplizer.cs:296

... When I track it down,is seems that the problem is that my child class is:

public class License {

public virtual Guid Id { get; private set; }
...
public virtual Guid Product_ID { get; set; }

}

But it is trying to put an instance of the Parent class in the Product_ID field. So it's actually trying to map Product_ID to an instance of Product class. So I end up with a Product that contains an array of Licenses, and it wants to have each License in the array contain an instance of the parent Product.

Solution 1

You can't use Inverse() together with an ordered collection (such as a list) - if you want to make it ordered then you need to omit the Inverse() and persist it from the parent item

Solution 2

Try mapping it as an unordered collection (bag):

HasMany<License>(x => x.Licenses)
    .Inverse()
    .Not.LazyLoad()
    .AsBag()
    .Cascade.AllDeleteOrphan()
    .ForeignKeyCascadeOnDelete()
    .KeyNullable()
    .KeyColumn("Product_ID")

Edited to add:

You shouldn't define the foreign key on the child object in addition to defining the many-to-one object through References. So License should be:

   public class License
   {
         ...
         public virtual Product {get; set;}
   }

Also, I assume you meant Product here and the cast is unnecessary because List<T> implements IList<T>:

   public class Product
   {
         ...
         public virtual IList<License>  Licenses { get; set; }
         public Product()
         {
            Licenses = new List<License>();
         }
   }

Hope this helps.

Comments

[Will I Am]

Thank you. That does work, however I would still like to understand how to handle the Index column in case I do want "AsList". I've seen plenty of examples using AsList() so I'm assuming it's not "disallowed".

[Will I Am]

Actually it doesn't work that as a Bag either (maybe a different issue?). I am getting a cast error. I updated the original post. I compiled nHibernate from source to get more information about the crash. It looks like its' trying to create an array of children products and create the Product_ID column as an instance of the parent class.

[Jamie Ide]

AsList maps the collection as an ordered collection and you have to have a database column to store the index. This is a good overview: blogs.hibernatingrhinos.com/nhibernate/archive/2008/06/12/…

[Will I Am]

Thanks Jamie, that does fix the problem with the AsBag(). AsList() I still have the null index error. But I will mark your answer as accepted. I hope someone will explain to me the AsList issue!

[Will I Am]

Thanks, i will read the post.. I think we crossed wires while posting.