How do I implement ChangeTime and ChangeUser columns using NHibernate?

Question

I\'m trying to use NHibernate with an existing database. In the data-model there is columns in each table that contains the time and username of the last update made to a ro

Answer 1

Mookid's answer is correct although I would like to point out that if one is using S#arp Architecture, the NHib configuration should be set up as follows:

<hibernate-configuration>
    <session-factory>
    ...
        <event type="pre-update">
            <listener class="MyListener, MyAssembly"/>
        </event>
        <event type="pre-insert">
            <listener class="MyListener, MyAssembly"/>
        </event>
    </session-factory>
</hibernate-configuration>

The event elements go into the session-factory element.

Answer 2

You should register a listener to the pre insert and pre update events. You can do it through your configuration like so:

<hibernate-configuration>
    ...
    <event type="pre-update">
        <listener class="MyListener, MyAssembly"/>
    </event>
    <event type="pre-insert">
        <listener class="MyListener, MyAssembly"/>
    </event>
</hibernate-configuration>

and then implement a listener - something like this (might not be entirely accurate - written off my memory):

public class MyListener : IPreUpdateEventListener, IPreInsertEventListener
{
    public bool OnPreUpdate(PreUpdateEvent evt)
    {
        if (evt.Entity is IHasLastModified)
            UpdateLastModified(evt.State, evt.Persister.PropertyNames);

        return false;
    }

    public bool OnPreInsert(PreInsertEvent evt)
    {
        if (evt.Entity is IHasLastModified)
            UpdateLastModified(evt.State, evt.Persister.PropertyNames);

        return false;
    }

    void UpdateLastModified(object[] state, string[] names)
    {
        var index = Array.FindIndex(names, n => n == "LastModified");

        state[index] = DateTime.Now;
    }
}

and do the same thing with the pre update event.

EDIT: This one takes care of insert as well as update and it seems to work.

Answer 3

Instead of using LIsteners, you can also use Interceptors: Audit changes using interceptor

Answer 4

Hey I just had to solve this on a project I am working on, here is my answer

public interface IDateModified
{
    DateTime Created { get; set; }
    DateTime Modified { get; set; }
}

public class CustomDefaultSaveOrUpdateEventListener 
    : DefaultSaveOrUpdateEventListener
{
    protected override object EntityIsPersistent(SaveOrUpdateEvent evt)
    {
        var entity = evt.Entity as IDateModified;
        if (entity != null)
        {
                entity.Modified = DateTime.Now;
        }

        return base.EntityIsPersistent(evt);
    }

    protected override object EntityIsTransient(SaveOrUpdateEvent evt)
    {
        var entity = evt.Entity as IDateModified;
        if (entity != null)
        {
            entity.Created = entity.Modified = DateTime.Now;
        }

        return base.EntityIsTransient(evt);
    }
}

Then in my configuration (I am using Fluent NHibernate to configure my unit tests in code)

configuration.EventListeners.SaveOrUpdateEventListeners 
= new ISaveOrUpdateEventListener[]
{
    new CustomDefaultSaveOrUpdateEventListener() 
};

AWESOMENESSSSSSSS!