Entity framework 4 POCO how to update an entity?

Question

This is a method for add/update an entity using Self Tracking Entities, what is the equivalent using POCO?

        public Hero SaveHero(Hero hero)
        {
            using (WarEntities model = new WarEntities())
            {
                if (hero.ChangeTracker.State == ObjectState.Added)
                {
                    model.Heroes.AddObject(hero);
                    model.SaveChanges();
                    hero.AcceptChanges();
                    return hero;
                }
                else if (hero.ChangeTracker.State == ObjectState.Modified)
                {
                    model.Heroes.ApplyChanges(hero);
                    model.SaveChanges();
                    return hero;
                }
                else
                    return null;
            }
        }

Answer 1

The most straightforward way to update an entity is to fetch it by Id, rewrite all the properties and call SaveChanges():

public Hero SaveHero(Hero hero)
{
    using (WarEntities model = new WarEntities())
    {
        Hero dbHero = model.Heroes.FirstOrDefault(h => h.Id == hero.Id);
        if (dbHero != null)
        {
            dbHero.Name = hero.Name;
            dbHero.OtherProperties = hero.OtherProperties;
            ...
            model.SaveChanges();
            return dbHero;
        }
        else
        {
            model.Heroes.AddObject(hero);
            model.SaveChanges();
            return hero;
        }
    }

However, you can avoid fetching the entity from the DB by attaching the POCO entity and changing it's state to Modified:

public Hero SaveHero(Hero hero)
{
    using (WarEntities model = new WarEntities())
    {
        model.Heroes.Attach(hero);
        var heroEntry = model.ObjectStateManager.GetObjectStateEntry(hero);
        heroEntry.ChangeState(EntityState.Modified);
        model.SaveChanges();
        return hero;
    }

Note that this method will only work if you already have this "hero" in the DB and are updating the existing entry. You will need a separate method for adding a new "hero".