String cstr = "User Id=snameche;Password=xxx;Host=localhost;Database=guce;Initial Schema=public";
                using (var connection = new PgSqlConnection(cstr))
                {
                    using (var contex = new guceEntities(connection))
                    {
                        contex.user_groups.Add(new user_groups { username = "Hawaii" , grp_id=10});
                        contex.SaveChanges();
                    }
                    using (var contex = new guceEntities(connection))
                    {
                        foreach (var destination in contex.user_groups)
                        {
                            Console.WriteLine(destination.username);
                        }
                    }
                }