private void SuaHocSinh()
{
HocSinhDTO hs = new HocSinhDTO();
hs.IDHocSinh = int.Parse(txtIDHocSinh.Text);
hs.HoTen = txtHoTen.Text;
hs.IDLop = (int)cboLop.SelectedValue;
hs.GioiTinh = rdbNam.Checked ? "Nam" : "Nữ";
hs.NgaySinh = dtpNgaySinh.Value.ToShortDateString();
hs.SDT = txtSDT.Text;
hs.DiaChi = txtDiaChi.Text;
HocSinhDAO.SuaHS(hs);
}