How to update an entity without a round-trip? (EF 4)

Question

I tried the following:

public void UpdatePlayer(int id)
{
    Player player = new Player() {ID  = id};
    player.Password = "12";
    Entities.Players.Attach(player);
    Entities.SaveChanges();
}

No change at the db.
What am I missing?

Answer 1

I think it might be because you're setting the values before you attach the object - the data context will not know what fields have changed. Try:

public void UpdatePlayer(int id)
{
    Player player = new Player() {ID  = id};
    Entities.Players.Attach(player);
    player.Password = "12";
    Entities.SaveChanges();
}

Answer 2

attach is used for entities that already exist in the database, but you have to attach first, and then edit it, as another poster pointed out. you should use .Add instead of .Attach if you are creating new items.

FYI Entity Framework 4 - AddObject vs Attach