.NET 添加购物代码

if (Session["User"] != null)
{
DataTable cart;
//判断购物车是否存在
if (Session["Cart"] == null)
{
//创建购物车
cart = CreateCart();
}
else
{
cart = (DataTable)Session["Cart"];
}
//判断书是否存在

DataView dvTemp = new DataView(cart);
dvTemp.RowFilter = "id=" + Convert.ToInt32(ViewState["id"].ToString());
if (dvTemp.Count == 0)
{
//加入商品
DataRow row = cart.NewRow();
row["id"] = (int)ViewState["id"];
row["isbn"] = lblISBN.Text;
row["title"] = lblBookName.Text;
row["unitPrice"] = decimal.