ASP.Net ขอความช่วยเหลือทีคะ เรื่องส่งค่าข้ามเพจ (Listbox ไปยัง Label อีกหน้า)

 string cn = ConfigurationManager.ConnectionStrings["sqlCon"].ToString();
        DataSet ds = new DataSet();

        protected void Page_Load(object sender, EventArgs e)
        {
            lbluser.Text = Session["username"].ToString();
            lbltype.Text = Session["TName"].ToString();

            

            if (!Page.IsPostBack)
            {

                string sql = "Select BNAME,BPrice from book where TID ='" + Session["TID"] + "'";
                SqlDataAdapter da = new SqlDataAdapter(sql, cn);
                da.Fill(ds, "Book");
                
                gv.DataSource = ds.Tables["Book"];
                gv.DataBind();

            }
        }


        int total = 0;
        int price = 0;
        int pricetotal = 0;
        protected void Button1_Click(object sender, EventArgs e) ปุ่มแสดงรายการใน listbox
        {
            ltblist.Items.Add(txtname.Text + " " + "จำนวน" + " " + txtunit.Text + " " + "เล่ม");
            
            string books = ltblist.Items.ToString();

            int unitprice = Convert.ToInt16(txtunitprice.Text);
            int unit = Convert.ToInt16(txtunit.Text);
            pricetotal = Convert.ToInt16(txttotal.Text);



            price = unit * unitprice;
            total += price;
            pricetotal += total;

            txttotal.Text = pricetotal.ToString();


        }


        protected void gv_SelectedIndexChanged(object sender, EventArgs e)
        {
            int index = gv.SelectedIndex;


            GridViewRow gvr = gv.Rows[index];
            txtname.Text = gvr.Cells[1].Text;
            txtunitprice.Text = gvr.Cells[2].Text;
            
        }

        protected void Button2_Click(object sender, EventArgs e) ปุ่มที่ไปเพจ2
        {
            Session["username"] = lbluser.Text;
            Session["TName"] = lbltype.Text;
            Session["books"] = ltblist.Items.ToString();
            Session["pricetotal"] = txttotal.Text;

            Response.Redirect("finish.aspx");
        }

    }