Question

I have two simple classes which reference each other as a one-to-many relationship defined below:

public class Project
{
    public virtual int Id { get; set; }
    public virtual string Name { get; set; }
    public virtual IList<Document> Documents { get; set; }
}

public class Document
{
    public virtual int Id { get; set; }
    public string FileName { get; set; }
}

And my mappings are defined as:

public class ProjectMapping : ClassMap<Project>
{
    public ProjectMapping()
    {
        Table("Projects");
        Id(x => x.Id).Column("Project_Id").GeneratedBy.TriggerIdentity();
        HasMany(x => x.Documents)
            .Table("Documents")
            .KeyColumn("Document_Project_Id")
            .Cascade.AllDeleteOrphan()
            .Not.KeyNullable();
        Map(x => x.Name).Column("Project_Name");
    }
}

public class DocumentMapping : ClassMap<Document>
{
    public DocumentMapping()
    {
        Table("Documents");
        Id(x => x.Id).Column("Document_Id").GeneratedBy.TriggerIdentity();
        Map(x => x.FileName).Column("Document_File_Name");
    }
}

Everything seems to be working fine, adding/updating documents and calling session.Save(project) reflects the correct changes in my database, however if I am to delete a document from a list of documents associated with a project and call session.Save(project) the deleted document never gets deleted from the database.

Any ideas why everything else would work except for delete?

EDIT:
My MVC 4 project is set up with Fluent NHibernate as follows:

public class SessionFactoryHelper
{
    public static ISessionFactory CreateSessionFactory()
    {
        var c = Fluently.Configure();
        try
        {
            //Replace connectionstring and default schema
            c.Database(OdbcConfiguration.MyDialect.
                ConnectionString(x =>
                x.FromConnectionStringWithKey("DBConnect"))
                .Driver<NHibernate.Driver.OdbcDriver>()
                .Dialect<NHibernate.Dialect.Oracle10gDialect>())
                .ExposeConfiguration(cfg => cfg.SetProperty("current_session_context_class", "web"));
            c.Mappings(m => m.FluentMappings.AddFromAssemblyOf<Project>());
            c.Mappings(m => m.FluentMappings.AddFromAssemblyOf<Document>());
        }
        catch (Exception ex)
        {
            Log.WriteLine(ex.ToString());
        }
        return c.BuildSessionFactory();
    }
}

public class MvcApplication : System.Web.HttpApplication
{
    public static ISessionFactory SessionFactory { get; private set; }

    protected void Application_Start()
    {
        AreaRegistration.RegisterAllAreas();

        WebApiConfig.Register(GlobalConfiguration.Configuration);
        FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
        RouteConfig.RegisterRoutes(RouteTable.Routes);
        BundleConfig.RegisterBundles(BundleTable.Bundles);
        AuthConfig.RegisterAuth();

        SessionFactory = SessionFactoryHelper.CreateSessionFactory();
    }

    protected void Application_BeginRequest(object sender, EventArgs e)
    {
        var session = SessionFactory.OpenSession();
        CurrentSessionContext.Bind(session);
    }

    protected void Application_EndRequest(object sender, EventArgs e)
    {
        var session = CurrentSessionContext.Unbind(SessionFactory);
        session.Dispose();
    }
}

My repository is defined as follows:

public class Repository<T> : IRepository<T>
{
    public virtual ISession Session
    {
        get { return MvcApplication.SessionFactory.GetCurrentSession(); }
    }

    public T FindById(int iId)
    {
        return Session.Get<T>(iId);
    }

    public void Save(T obj)
    {
        using (var transaction = Session.BeginTransaction())
        {
            try
            {
                Session.Save(obj);
                transaction.Commit();
            }
            catch (Exception ex)
            {
                transaction.Rollback();

                Log.WriteLine(ex.ToString());
            }
        }
    }

    public T SaveOrUpdate(T obj)
    {
        using (var transaction = Session.BeginTransaction())
        {
            try
            {
                Session.SaveOrUpdate(obj);
                transaction.Commit();
            }
            catch (Exception ex)
            {
                transaction.Rollback();

                Log.WriteLine(ex.ToString());
            }
        }

        return obj;
    }

    public T Update(T obj)
    {
        using (var transaction = Session.BeginTransaction())
        {
            try
            {
                Session.Update(obj);
                transaction.Commit();
            }
            catch (Exception ex)
            {
                transaction.Rollback();

                Log.WriteLine(ex.ToString());
            }
        }

        return obj;
    }
}

I have 2 Actions defined in my ProjectsController as follows:

private IRepository<Project> repository;

public ProjectsController()
{
    repository = new Repository<Project>();
}

public ActionResult Edit(int iId)
{
    Project project = repository.FindById(iId);

    if (project == null)
        return HttpNotFound();

    return View(project);
}

[HttpPost]
public ActionResult Edit(Project project)
{
    project = repository.Update(project);

    return View(project);
}

If I am to delete a document in my first action (without HttpPost):

project.Documents.RemoveAt(0);
repository.Update(project);

The correct row is removed from the database.
However, if I am to do the very same in the action with HttpPost attribute, the row is never removed.

Also I should note that if I add a document to project.Documents in the action with HttpPost attribute, repository.Update(project) successfully adds the row with the correct foreign key reference to the project. This is only failing when I remove a document.

Answer 1

The cascade setting seems to be correct. The issue mentioned could be elsewhere:

however if I am to delete a document from a list of documents associated with a project

Suspected to me is a session flush mode, or missing explicit call to update parent entity Project, which was previously detached. Assure:

First, that the Flush() was called. In case that project instance is still kept in Session, the default behavior of flushing could be changed. (e.g. session.FlushMode = FlushMode.Never; or Commit without having transaction…)

// 1) checking the explicit Flush()
project.Documents.Remove(doc);
Session.Flush(); // this will delete that orphan

The second could be evicted project instance, needing the explicit update call

// 2) updating evicted project instance
project.Documents.Remove(doc);
Session.Update(project);
//Session.Flush(); // Session session.FlushMode = FlushMode.Auto

The setting inverse will in this case (only) help to reduce one trip to database with UPDATE statement, resetting reference to doc.Project = null, then executing DELETE.