Setting the update timestamp in Entity Framework

Here is how the other two concepts are put into practice, with the following things to keep in mind:

• Prior to calling SaveChanges, be careful to either setup proxies that automatically detect changes or manually detect changes (). Otherwise, the object state will beEntityState.Unmodified , and no change will be made to the latest changed timestamp.
• When the object is first created, I've changed the code to include set the latest modified timestamp (EntityState.Added )

The Law

public interface IHasLastModified
{
    DateTime? LastModified { get; set; }
}

public class MyClass : IHasLastModified
{
    public virtual int Id { get; set; }

    public virtual string SomeOtherProperty { get; set; }

    public virtual DateTime? LastModified { get; set; }
}

public class MyContext : DbContext
{
    public override int SaveChanges()
    {            
        DateTime now = DateTime.UtcNow;
        foreach (ObjectStateEntry entry in (this as IObjectContextAdapter).ObjectContext.ObjectStateManager.GetObjectStateEntries(EntityState.Added | EntityState.Modified))
        {
            if (!entry.IsRelationship)
            {
                IHasLastModified lastModified = entry.Entity as IHasLastModified;
                if (lastModified != null)
                    lastModified.LastModified = now;
            }
        }

        return base.SaveChanges();
    }