public void ChangeMDIForm(Page page)
        {
            if (currentPage == page)
            {
                return;
            }

            //currentForm.Close();
            currentForm.Dispose();

            Form newFormPage;

            switch (page)
            {
            case Page.Home:
                newFormPage = new Staff.StaffHome();
                break;

            case Page.Profile:
                newFormPage = new Staff.StaffProfile();
                break;

            case Page.PlayerAccount:
                newFormPage = new Staff.StaffPlayerAccount();
                break;

            case Page.PlayerAccount_inSide:
                newFormPage = new Staff.StaffPlayerAccount_inSide();
                break;

            case Page.PointCard:
                newFormPage = new Staff.StaffPointCard();
                break;

            case Page.PointCard_inSide:
                newFormPage = new Staff.StaffPointCard_inSide();
                break;

            case Page.ReceiveProblems:
                newFormPage = new Staff.StaffReceiveProblems();
                break;

            case Page.Setting:
                newFormPage = new Staff.StaffSetting();
                break;

            default:
                MessageBox.Show("Unexpect switch flow.");
                return;
            }

            newFormPage.MdiParent = this;
            newFormPage.Dock      = DockStyle.Fill;
            newFormPage.Show();

            currentForm = newFormPage;
            currentPage = page;
        }
        private void StaffMenu_Load(object sender, EventArgs e)
        {
            Staff.StaffHome staffHome = new Staff.StaffHome
            {
                MdiParent = this,
                Dock      = DockStyle.Fill
            };
            staffHome.Show();

            currentForm = staffHome;
            currentPage = Page.Home;

            RefreshPage();
        }