private void SubjectDetailGUI_Load(object sender, EventArgs e)
        {
            string text = label1.Text;

            text       += SubjectDAO.getSubjectName_Hoang(subid);
            label1.Text = text + " is " + count + " students";
            txt1.Text   = getTest1(subid);
            txt2.Text   = getTest2(subid);
            txt3.Text   = getTest3(subid);
            txt4.Text   = getFinal(subid);
        }