NHibernate IPostInsertEventListener : Insert executed multiple times - events

Question

I am trying to test a simple NHibernate-based auditing mechanism that stores one row per changed property into a changelog table. What it actually does, is perform the actual insert statement as expected and perform the audit logging twice.
So, this is what I do:
string connectionString = #"Data Source=.\SQLEXPRESS;Initial Catalog=audittest;Integrated Security=SSPI;";
FluentConfiguration config = Fluently.Configure().Database(MsSqlConfiguration.MsSql2008
.ConnectionString(c => c.Is(connectionString)).ShowSql())
.Mappings(x => x.FluentMappings.Add<Class1ClassMap>())
.Mappings(x => x.FluentMappings.Add<ChangeLogMap>())
.ExposeConfiguration(cfg =>
{
NHibernateAuditListener listener = new NHibernateAuditListener();
cfg.AppendListeners(ListenerType.PostInsert, new[] { listener });
});
ISessionFactory sf = config.BuildSessionFactory();
ISession session = sf.OpenSession();
using (ITransaction tr = session.BeginTransaction())
{
session.Save(new Class1()
{
FirstName="Peter",
LastName="Pan",
Id=100
});
tr.Commit();
}
EDIT:
Altered the logging code to something simple to see the failure:
public void OnPostInsert(PostInsertEvent #event)
{
if (#event.Entity is IAuditable)
{
Console.WriteLine("----write audit----");
for (int index = 0; index < #event.State.Length; index++)
Console.WriteLine("----store changes of property {0}----",
#event.Persister.PropertyNames[index]);
}
}
This generates the following output:
NHibernate: INSERT INTO "Class1" (FirstName, LastName, Id) VALUES (#p0, #p1, #p2); #p0 = 'Peter' [Type: String (0)], #p1 = 'Pan' [Type: String (0)], #p2 = 1 [Type: Int64 (0)]
----write audit----
----store changes of property FirstName----
----store changes of property LastName----
----write audit----
----store changes of property FirstName----
----store changes of property LastName----
As you see, it's not the EventHandler code that's erroneous, but the framework calling it that behaves unexpectedly (calling the OnPostInsert method twice). Any ideas why this is happening?
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Answer 1

Okay everybody, the problem exists in the detail of the handling within the programm. You are building up a FluentConfiguration-instance which on the fly creates the the basic NHibernate configuration.
This is done on the call of these 2 lines (variable config is of type FluentConfiguration):
new SchemaExport(config.BuildConfiguration()).Create(true, true);
and
ISessionFactory sf = config.BuildSessionFactory();
The FluentConfiguration caches the first created instance and reuses it for creating the new instance for the ISessionFactory-instance. On both calls the ExposeConfiguration of FluentConfiguration instance is called. So there are 2 instances of the NHibernateAuditListener within the session that is persisting the data.
Try it like this:
string connectionString = #"Data Source=.\SQLEXPRESS;Initial Catalog=audittest;Integrated Security=SSPI;";
var config = Fluently.Configure().Database(MsSqlConfiguration.MsSql2008
.ConnectionString(c => c.Is(connectionString)).ShowSql())
.Mappings(x => x.FluentMappings.Add<Class1ClassMap>())
.Mappings(x => x.FluentMappings.Add<ChangeLogMap>())
.ExposeConfiguration(cfg =>
{
NHibernateAuditListener listener = new NHibernateAuditListener();
cfg.AppendListeners(ListenerType.PostInsert, new[] { listener });
})
.BuildConfiguration();
new SchemaExport(config).Create(true, true);
Console.WriteLine("----------------------------------------------");
ISessionFactory sf = config.BuildSessionFactory();
ISession session = sf.OpenSession();
using (ITransaction tr = session.BeginTransaction())
{
session.Save(new Class1()
{
FirstName="Peter",
LastName="Pan",
Id=100
});
tr.Commit();
}
Within config you have now the real NHibernate Configuration instance, with only one Listener registered.
Got it?!