Question

I am using NHibernate 3.1 and Fluent NHibernate as ORM in my project. I need to have a property of a POCO ignored by Fluent NHibernate. At first, my post might look as exact duplicate of this question, but it is not.

My complications come first from the fact that the POCOs are defined in a different assembly than the mapping and I am using fluent mappings for my POCOs. I have additional requirement not to write ingore-property code where the session factory configuration takes place (this happens at a centralized place outside the modules), but as part of the module that defines the mappings. Ideally, I believe the right place would be the concrete ClassMap implementation, since it knows exactly how to describe a POCO to the ORM.

However, I am stuck on this mainly because this is my first impact with NHibernate and its fluent API. Up to now I am having very good impression of its capabilities and extensibility, and I hope there is a way to achieve my requirement in a way that the mapping related code is encapsulated in its corresponding module.

Here is my configuration, from a centralized place:

List<Assembly> assemblies = GetModules().Select(x => x.GetType().Assembly).ToList();

ISessionFactory nhibernateSessionFactory = Fluently
    .Configure()
    .Mappings(m => assemblies.ForEach(asm => m.FluentMappings.AddFromAssembly(asm)))
    .Database(
        MsSqlConfiguration.MsSql2005
            .ShowSql()
            .ConnectionString(DatabaseConfig.Instance.ConnectionString))
    .ExposeConfiguration(c => new SchemaUpdate(c).Execute(true, true))
    .BuildSessionFactory();

I use standard class mappings that inherit from ClassMap:

public class User
{
    public virtual int ID { get; set; }
    public virtual String Username { get; set; }
    public virtual String Password { get; set; }
    public virtual DateTime DateCreated { get; set; }
    public virtual DateTime DateModified { get; set; }

    // Must ignore
    public string ComputedProperty  { get { ... } }
}

public class UserMap : ClassMap<User>
{
    public UserMap()
    {
        Table("User");
        Id(x => x.ID).GeneratedBy.Identity();
        Map(m => m.Username).Not.Nullable().Length(255).UniqueKey("User_Username_Unique_Key");
        Map(m => m.Password).Not.Nullable().Length(255);
        Map(m => m.DateCreated).Not.Nullable();
        Map(m => m.DateModified).Not.Nullable();
    }
}

Answer 1

I think you are right that the ClassMap is the best place to ignore this property.

Example:

.Override<Shelf>(map =>  
{  
  map.IgnoreProperty(x => x.YourProperty);
});

Documentation: https://github.com/jagregory/fluent-nhibernate/wiki/Auto-mapping#ignoring-properties

As far as getting the mappings from another assembly, it should be as easy as something like this (depending on your current configuration):

.Mappings(m =>
              {
                  m.FluentMappings.AddFromAssemblyOf<ProvideClassFromYourOtherAssembly>();
              });