private void loginButton_Click(object sender, EventArgs e)
        {
            LoginForm log = new LoginForm();

            log.ShowDialog();

            if (GlobalConfig.GuestUser != -1) // Guest logged in
            {
                GuestForm form = new GuestForm();
                form.ShowDialog();
            }
            else if (GlobalConfig.OwnerUser != -1) // Owner logged in
            {
                BusOwnerForm form = new BusOwnerForm();
                form.ShowDialog();
            }
        }
 private void buyTicket_Click(object sender, EventArgs e)
 {
     if (GlobalConfig.GuestUser != -1)
     {
         int counter = 0;
         foreach (Button but in TangDuoi.Controls)
         {
             if (but.BackColor == Color.Yellow)
             {
                 GlobalConfig.AddTicket(bus, but.Text, but.Name);
                 counter++;
             }
         }
         foreach (Button but in TangTren.Controls)
         {
             if (but.BackColor == Color.Yellow)
             {
                 GlobalConfig.AddTicket(bus, but.Text, but.Name);
                 counter++;
             }
         }
         if (counter > 0)
         {
             MessageBox.Show("Thành công!");
         }
         else
         {
             MessageBox.Show("Bạn chưa chọn ghế");
         }
         this.Close();
         GuestForm form = new GuestForm();
         form.ShowDialog();
     }
     else
     {
         MessageBox.Show("Vui lòng đăng nhập!");
         LoginForm form = new LoginForm();
         form.ShowDialog();
     }
 }