Nhibernate Remove child collection without having property in the parent object - nhibernate

Question

Suppose I have the following model
public class Customer
{
public virtual Guid Id { get; set; }
public virtual string Name { get; set; }
}
public class ActivityLog
{
public virtual Guid Id { get; set; }
public virtual Guid CustomerId { get; set; }
public virtual Customer Customer { get; set; }
public virtual DateTime ActivityDate { get; set; }
}
I would like to be able to remove customer and all corresponding ActivityLog items, by calling
session.Delete(customer);
What I don't want to is to have a property
List<ActivityLog> Logs in my Customer class. Is it possible to achieve in Nhibernate? I have tried EF, and it works there, but in HN getting reference constraint exception.
My mappings:
public class CustomerMap : ClassMapping<Customer>
{
public CustomerMap()
{
Id(x => x.Id, map => map.Generator(Generators.GuidComb));
Property(x => x.Name);
}
}
public class ActivityLogMap : ClassMapping<ActivityLog>
{
public ActivityLogMap()
{
Id(x => x.Id, map => map.Generator(Generators.GuidComb));
Property(x => x.ActivityDate);
ManyToOne(x => x.Customer, mapping =>
{
mapping.Class(typeof(Customer));
mapping.Column("CustomerId");
});
}
}
Maybe possible to have some extension hook and inspect mapping and do it manually for Nhibernate?
Edit: Here how it works with EF
public class CustomerEFMap : EntityTypeConfiguration<Customer>
{
public CustomerEFMap()
{
ToTable("Customer");
HasKey(x => x.Id);
Property(x => x.Name);
}
}
public class ActivityLogEFMap : EntityTypeConfiguration<ActivityLog>
{
public ActivityLogEFMap()
{
ToTable("ActivityLog");
HasKey(x => x.Id);
HasRequired(x => x.Customer).WithMany().HasForeignKey(x => x.CustomerId);
}
}
using (var context = new ObjectContext())
{
var customer = context.Set<Customer>().Find(id);
context.Set<Customer>().Remove(customer);
context.SaveChanges();
}
Having Customer and corresponding ActivityLog in DB, removes both

Answer 1

I would like to be able to remove customer and all corresponding
ActivityLog items, by calling
session.Delete(customer);
What I don't want to is to have a property List Logs in
my Customer class. Is it possible to achieve in Nhibernate?
NO. Impossible, not intended, not supported. NHibernate is ORM tool and will/can care about relations. Without relations, no care (no cascading)
But, we can always hide that List Property by making it protected
public class Customer
{
public virtual Guid Id { get; set; }
public virtual string Name { get; set; }
// HIDDEN in fact from consumers, managed by NHibernate
protected virtual IList<ActivitLog> { get; set; }
}
and the mapping with cascade in place - will do what is required.

Answer 2

As Radim Köhler states, I don't think there's any simple way to map the behaviour of a cascade without actually having the relationship. But as your reason for this is a plugin-based architecture, making use of a partial class might be what you need.
You can include the collection of ActivityLogs as a protected collection as part of a partial class in the plugin DLL. If your mapping then maps the collection, deleting the Customer will delete the ActivityLogs.
The following example should work - note that I'm using FluentNhibernate for the mapping.
This solution does rely on you be able to mark the Customer class as partial.
using FluentAssertions;
using FluentNHibernate;
using FluentNHibernate.Cfg;
using FluentNHibernate.Cfg.Db;
using FluentNHibernate.Mapping;
using NHibernate.Linq;
using NHibernate.Tool.hbm2ddl;
using NUnit.Framework;
using System;
using System.Collections.Generic;
namespace MapTest
{
public partial class Customer
{
public virtual Guid Id { get; set; }
public virtual string Name { get; set; }
}
public class ActivityLog
{
public virtual Guid Id { get; set; }
public virtual Customer Customer { get; set; }
public virtual DateTime ActivityDate { get; set; }
}
public class CustomerMap : ClassMap<Customer>
{
public CustomerMap()
{
Id(x => x.Id).GeneratedBy.Guid();
Map(x => x.Name);
HasMany<ActivityLog>(Reveal.Member<Customer>("ActivityLogs")).Cascade.All();
}
}
public class ActivityLogMap : ClassMap<ActivityLog>
{
public ActivityLogMap()
{
Id(x => x.Id).GeneratedBy.Guid();
Map(x => x.ActivityDate);
References(x => x.Customer);
}
}
// Part of your plugin DLL
public partial class Customer
{
protected virtual IList<ActivityLog> ActivityLogs { get; set; }
}
[TestFixture]
public class PartialClassCascade
{
[Test]
public void RunOnceToSetupDb()
{
Fluently.Configure()
.Database(MsSqlConfiguration.MsSql2012.ConnectionString(#"Data Source=(localdb)\MSSQLLocalDB;Initial Catalog=MapTest;Integrated Security=True;Connect Timeout=30;Encrypt=False;TrustServerCertificate=False;ApplicationIntent=ReadWrite;MultiSubnetFailover=False"))
.Mappings(m => m.FluentMappings.AddFromAssemblyOf<CustomerMap>())
.ExposeConfiguration(cfg => new SchemaUpdate(cfg).Execute(false, true))
.BuildSessionFactory();
}
[Test]
public void DeletingCustomerWithActivityLogs()
{
var sessionFactory = Fluently.Configure()
.Database(MsSqlConfiguration.MsSql2012.ConnectionString(#"Data Source=(localdb)\MSSQLLocalDB;Initial Catalog=MapTest;Integrated Security=True;Connect Timeout=30;Encrypt=False;TrustServerCertificate=False;ApplicationIntent=ReadWrite;MultiSubnetFailover=False"))
.Mappings(m => m.FluentMappings.AddFromAssemblyOf<CustomerMap>())
.BuildSessionFactory();
using (var session = sessionFactory.OpenSession())
using (var tx = session.BeginTransaction())
{
session.CreateQuery("delete ActivityLog a").ExecuteUpdate();
session.CreateQuery("delete Customer c").ExecuteUpdate();
tx.Commit();
}
var homerId = default(Guid);
using (var session = sessionFactory.OpenSession())
using (var tx = session.BeginTransaction())
{
var homer = new Customer
{
Name = "Homer Simpson"
};
var monty = new Customer
{
Name = "Monty Burns"
};
session.Save(homer);
session.Save(monty);
homerId = homer.Id;
var activityLog1 = new ActivityLog
{
Customer = homer,
ActivityDate = DateTime.Now,
};
var activityLog2 = new ActivityLog
{
Customer = monty,
ActivityDate = DateTime.Now.AddDays(1),
};
session.Save(activityLog1);
session.Save(activityLog2);
tx.Commit();
}
using (var session = sessionFactory.OpenSession())
using (var tx = session.BeginTransaction())
{
var customer = session.Get<Customer>(homerId);
session.Delete(customer);
tx.Commit();
}
using (var session = sessionFactory.OpenSession())
using (var tx = session.BeginTransaction())
{
var customers = session.Query<Customer>();
var activityLogs = session.Query<ActivityLog>();
customers.Should().HaveCount(1);
activityLogs.Should().HaveCount(1);
}
}
}
}