private void cbbTenCongTrinh_SelectedIndexChanged(object sender, EventArgs e)
{
_luongCongTrinhDangChon = ctbll.layLuongCT_CongTrinh(cbbTenCongTrinh.Text);
dtpNgayBatDau.Value = ctbll.layNgayBD_CT(cbbTenCongTrinh.Text);
dtpNgayKetThuc.Value = ctbll.layNgayKT_CT(cbbTenCongTrinh.Text);
}