Entity Framework/SQL2008 – How to Automatically Update LastModified fields for Entities?

I know I’m a little late to the party, but I just solved this for a project I’m working on and thought I’d share my solution.

First, to make the solution more re-usable, I created a base class with the timestamp properties:

public class EntityBase
{
    public DateTime? CreatedDate { get; set; }
    public DateTime? LastModifiedDate { get; set; }
}

Then I overrode the SaveChanges method on my DbContext:

public class MyContext : DbContext
{
    public override int SaveChanges()
    {
        ObjectContext context = ((IObjectContextAdapter)this).ObjectContext;

        //Find all Entities that are Added/Modified that inherit from my EntityBase
        IEnumerable<ObjectStateEntry> objectStateEntries =
            from e in context.ObjectStateManager.GetObjectStateEntries(EntityState.Added | EntityState.Modified)
            where
                e.IsRelationship == false &&
                e.Entity != null &&
                typeof(EntityBase).IsAssignableFrom(e.Entity.GetType())
            select e;

        var currentTime = DateTime.Now;

        foreach (var entry in objectStateEntries)
        {
            var entityBase = entry.Entity as EntityBase;

            if (entry.State == EntityState.Added)
            {
                entityBase.CreatedDate = currentTime;
            }

            entityBase.LastModifiedDate = currentTime;
        }

        return base.SaveChanges();
    }
}