private void LoginButton_Click(object sender, EventArgs e)
        {
            Rank loggedInRank = reservationSystem.Login(UsernameTextBox.Text, PasswordTextBox.Text);

            if (loggedInRank == Rank.Manager)
            {
                this.Hide();
                var mainPage = new MainPage_Manager(reservationSystem);
                mainPage.Closed += (sender2, args) => this.Close();
                mainPage.Show();
            }
            else if (loggedInRank == Rank.Salesman)
            {
                this.Hide();
                var mainPage = new MainPage_Salesman(reservationSystem);
                mainPage.Closed += (sender2, args) => this.Close();
                mainPage.Show();
            }
        }
        private void LoginButton_Click(object sender, EventArgs e)
        {
            Rank loggedInRank = reservationSystem.Login(UsernameTextBox.Text, PasswordTextBox.Text);

            if (loggedInRank == Rank.Manager)
            {
                this.Hide();
                var mainPage = new MainPage_Manager(reservationSystem);
                mainPage.Closed += (sender2, args) => this.Close();
                mainPage.Show();
            }
            else if (loggedInRank == Rank.Salesman)
            {

                this.Hide();
                var mainPage = new MainPage_Salesman(reservationSystem);
                mainPage.Closed += (sender2, args) => this.Close();
                mainPage.Show();
            }
        }