Entity Framework UpdateException in SqlCe Database.

Question

Hi, I'm using SQLCE database and Entity Framework 4 as my Data Access in a Winforms project.

Create a class library to store all my Queries, Inserts, Updates, Deletes. I want to work in a disconnected environment without change tracking or contexts loaded, so i use code like this for a query (example):

public List<UserPlaylists> GetUserPlayLists()
{
    using (var dbUserPlaylists = new PlaylistsEntities())
    {
        List<UserPlaylists> playLists = dbUserPlaylists.UserPlaylists
            .Include("PlaylistSongs").ToList();

        playLists.ForEach(dbUserPlaylists.Detach);

        return playLists;
    }
}

OK, context is disposed and Entities are detached. I use the List<> to bind to a BindindSource and this to a XtraGrid (DevExpress). Now I create a new playlist and want to update or Insert the PlayLists binded to the grid. I found from a post here this very nice extension class, created for the EF 1 but it seems it should work for EF 4 too. Tried some operations without this class too and I'm keep getting the same UpdateException with InnerException message:

{"Server-generated keys and server-generated values are not supported by SQL Server Compact."}

My code while Insert or Update:

public void SaveUserPlayLists(IList list)
{
    using (var db = new PlaylistsEntities())
    {
        foreach (UserPlaylists playlist in list)
        {
            playlist.AttachGraph(db, () => new PlaylistsEntities());
        }
        db.SaveChanges();
    }
}

I can't seem to explain what it needs exactly. I used LINQ to SQL for a project of mine before but i want to use EF 4 now for my new projects.

Any help or idea's would be really helpful. Thank you in advance.