private void thong_ke_gioi_tinh()
{
var v_dt = m_data_set.Tables[0].AsEnumerable();
m_lbl_so_nv_nam.Text = "Nam: " + v_dt.Where(x => x.Field<string>("GIOI_TINH") == "Y").Count();
m_lbl_so_nv_nu.Text = "Nữ: " + v_dt.Where(x => x.Field<string>("GIOI_TINH") == "N").Count();
}