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.

Answer 1

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();
}