//lay so luong sach nhap trong thang
        int GetSLNhap(int thang, int nam, string masach)
        {
            int       soluongnhap = 0;
            SachBUS   objSach     = new SachBUS();
            DataTable dtSLNhap    = objSach.GetSoLuongNhap(thang, nam, masach);

            for (int j = 0; j < dtSLNhap.Rows.Count; j++)
            {
                soluongnhap += int.Parse(dtSLNhap.Rows[j]["soluong"].ToString());
            }
            return(soluongnhap);
        }