public List<User> FindAllByTask(int id)
        {
            List<User> users = new List<User>();

            using (var db = new SqlConnection(connectionString))
            {
                string query = "select u.id, u.firstname, u.lastname, u.email, u.created from " + A_TABLE_TASK + " sp, " + TABLE_NAME + " u where sp.attachableobject_id = u.id and task_id = @id";
                SqlCommand command = new SqlCommand(query, db);
                command.Parameters.AddWithValue("@id", id);

                try
                {
                    db.Open();
                    SqlDataReader reader = command.ExecuteReader();

                    while (reader.Read())
                    {
                        var idd = (int)reader[0];
                        var firstname = (string)reader[1];
                        var lastname = (string)reader[2];
                        var email = (string)reader[3];
                        var created = (DateTime)reader[4];
                        users.Add(new User(idd, firstname, lastname, email, null, created));
                    }

                    reader.Close();

                    return users;
                }
                catch (Exception ex)
                {
                    Console.WriteLine(ex.Message);
                    return users;
                }
            }
        }