public bool AddUser(User a_user)
        {
            if (IsUsernameUnique(a_user.Name) && a_user.HasCorrectDetails)
            {
                //subscribe to user events
                a_user.AddSubscriber(this);

                //add it to array
                m_users.Add(a_user);

                //notify subscribers
                this.NotifySubscribersChangeMade(a_user);

                return true;
            }

            return false;
        }