private void delete_du_lieu_cu() { US_GD_CAC_KHOAN_TIEN_KHAC v_us = new US_GD_CAC_KHOAN_TIEN_KHAC(); v_us.DeleteDuLieuCu(lay_thang(), lay_nam(), Convert.ToDecimal(m_cmb_khoan_tien.SelectedValue)); }