Mapping exception when using Fluent NHibernate

Question

When I tried to perform CRUD operations on a POCO against a database, I got an exception: NHibernate Mapping Exception: No persister for: MyNamespace.Model.User.

Here is my code:

namespace MyNamespace.Model
{
    public interface IModel<TID>
    {
        TID ID { get; set; }
    }

    public class User : IModel<int>
    {
        public virtual int ID { get; set; }
        public virtual string Name { get; set; }
    }
}

and here is my mapping

namespace MyNamespace.Model.Mapping
{
    public class UserMap : ClassMap<User>
    {
        public UserMap()
        {
            Table("User");
            Id(x => x.ID);
            Map(x => x.Name)
                .Length(255)
                .Unique()
                .Not.Nullable();
        }
    }
}

In my configuration file I have added the assembly mapping:

<hibernate-configuration xmlns="urn:nhibernate-configuration-2.2">
    <session-factory>
        ...
        <mapping assembly="MyNamespace" /> 
    </session-factory>
</hibernate-configuration>

I know that such issue occurs if using hbm files, when not set as embedded resources. But in my case I am using Fluent NHibernate where no such files are used. I also read here, that the Mapping classes should be public - I have done that as you can see. All my properties of the model class are virtual (to allow proxies to do their magic). I am absolutely unaware of what I am missing here and I'd be glad to hear any suggestions for this issue.

Diego Mijelshon · Accepted Answer · 2012-03-06 02:18:11Z

2

The <mapping> element is for hbm resources, not fluent mappings.

This is straight from the Fluent NHibernate docs:

private static ISessionFactory CreateSessionFactory()
{
  return Fluently.Configure()
    .Database(
      SQLiteConfiguration.Standard
        .UsingFile("firstProject.db")
    )
    .Mappings(m =>
      m.FluentMappings.AddFromAssemblyOf<Program>())
    .BuildSessionFactory();
}

answered Mar 6, 2012 at 2:18

Diego Mijelshon

52.7k16 gold badges119 silver badges159 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

stackh34p Over a year ago

At the moment I cannot try your solution, but I am curious to why this might be the reason. I am configuring my session factory in the same old-fashioned way using the configuraton.BuildSessionFactory(). Maybe the mapping classes are not scanned taking into account the app.config settings? It is a little confusing having different ways to configure the same thing with the same information, and as result it works differently.

Diego Mijelshon Over a year ago

NHibernate does not know about Fluent. Therefore, NH's native config cannot possibly read Fluent mappings.

stackh34p Over a year ago

Thank you for the answer and clarifications. Now I realize that fluent maintains the mapping information in a completely different manner, probably incompatible with the hbm-dedicated storage. I just had assumed wrongly that Fluent would take into account assemblies passed in the app.config.

Sly · Accepted Answer · 2012-03-06 09:03:10Z

1

This error message most of the time means that NHibernate has no mappings for entity you are trying to save. So configure your session factory with FluentNHibernate to provide mappings for it.

answered Mar 6, 2012 at 9:03

Sly

15.3k13 gold badges64 silver badges90 bronze badges

Collectives™ on Stack Overflow

Mapping exception when using Fluent NHibernate

2 Answers 2

3 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related