public FromThemSinhVien(string maLop)
{
InitializeComponent();
txtMaLop.Text = maLop;
txtMaSV.Text = SinhVien.TaoMaSV(maLop);
txtEmail.Text = (txtMaSV.Text.Trim() == "") ? KeyConst.EmailTag.Student : txtMaSV.Text.Trim() + KeyConst.EmailTag.Student;
}