Fluent-NHibernate and persisting DateTime automatically

Question

I'm using S#arpArchitecture (ASP.NET MVC and Fluent NHibernate). I have an entity as follows:

public class User : Entity
{
    public User(){}
    public User(string firstName, string lastName)
    {
        FirstName = firstName;
        LastName = lastName;
    }

    public virtual string FirstName { get; set; }
    public virtual string LastName { get; set; }
    public virtual DateTime? LastUpdate{ get; set; }
}

I will call the SaveOrUpdate method on my repository class that will persist this User object. It works. How would i persist the LastUpdate property automatically with the latest date and time? I could override the SaveOrUpdate method in my repository by always setting the LastUpdate property to the current date and time but that does not seem to be correct because if there's nothing changed in my entity, I don't think NHibernate will persist my object back to the DB and forcing the setting of this property will always make it persist back.

I only want this LastUpdate property set if something else has changed in my entity.

Answer 1

You should use an NHibernate Interceptor to accomplish this. Override OnFlushDirty in your interceptor implementation to set the LastUpdate property only when something has changed (i.e. your object is dirty).

Answer 2

I'm going to point to another StackOverflow question that I think answers my question.