title: NHibernate dynamic-update fails to update data changed in interceptor
body: <p>If I set dynamic-update=true I've found that fields updated in my Interceptor do not get included in the update statement that goes to the database. When I set it to false all the columns including the time stamp get updated. I really want to use dynamic update.</p>
  
  <pre><code>public class Interceptor : EmptyInterceptor
  {
    public override Boolean OnFlushDirty(object entity, object id, object[] state,
      object[] previousState, string[] propertyNames, IType[] types)
    {
      var auditEntity = entity as BaseAuditEntity;
  
      if (auditEntity != null)
      {
        var now = DateTime.Now;
        var index = Array.IndexOf(propertyNames, "LastModifiedTimestamp");
        state[index] = now;
        auditEntity.LastModifiedTimestamp = now;
      }
      return base.OnFlushDirty(entity, id, state, previousState, propertyNames, types);
    }
  
  }
  </code></pre>
  
  <p>I thought that this line would have marked my the last modified column as dirty.</p>
  
  <pre><code>auditEntity.LastModifiedTimestamp = now;
  </code></pre>
  
  <p>Is there something I should do in my interceptor to mark the time stamp field as dirty?</p>