public List <ThongKeBEAN> getListThongKeTheoThang(long thang, long nam)
        {
            string       sql = "SELECT * FROM Qtk WHERE MONTH(NgayBan) = @thang AND YEAR(NgayBan) = @nam";
            SqlCommand   cmd = new SqlCommand(sql, DungChung.cn);
            SqlParameter ts  = new SqlParameter("@thang", thang);
            SqlParameter ts2 = new SqlParameter("@nam", nam);

            cmd.Parameters.Add(ts);
            cmd.Parameters.Add(ts2);
            SqlDataReader      rs = cmd.ExecuteReader();
            List <ThongKeBEAN> ds = new List <ThongKeBEAN>();

            while (rs.Read())
            {
                string      tenHang    = rs["TenHang"].ToString();
                string      gia        = rs["Gia"].ToString();
                string      soLuongMua = rs["SoLuongMua"].ToString();
                string      thanhTien  = rs["ThanhTien"].ToString();
                string      ngayBan    = rs["NgayBan"].ToString();
                ThongKeBEAN thongKe    = new ThongKeBEAN(tenHang, long.Parse(gia), long.Parse(soLuongMua), long.Parse(thanhTien), DateTime.Parse(ngayBan));
                ds.Add(thongKe);
            }
            rs.Close();
            return(ds);
        }
        public List <ThongKeBEAN> getListThongKe(string ma)
        {
            string     sql = "SELECT * FROM ThongKe WHERE MaHang = @maHang ";
            SqlCommand cmd = new SqlCommand(sql, DungChung.cn);

            cmd.Parameters.Add(new SqlParameter("@maHang", ma));
            SqlDataReader      rs = cmd.ExecuteReader();
            List <ThongKeBEAN> ds = new List <ThongKeBEAN>();

            while (rs.Read())
            {
                string      TenHang    = rs["TenHang"].ToString();
                string      SoLuongMua = rs["SoLuongMua"].ToString();
                string      ThanhTien  = rs["ThanhTien"].ToString();
                ThongKeBEAN ban        = new ThongKeBEAN(TenHang, long.Parse(SoLuongMua), long.Parse(ThanhTien));
                ds.Add(ban);
            }
            rs.Close();
            return(ds);
        }