//如：
Session["orders"] = hs;                 //key-->id,value-->Orders
string curId = tempStr;
if(hs.Keys.Contains(curId))
{
  ((Orders)hs[curId]).BuyCount += 1;   //Orders是购物车中的订单实体类
}
else
{
  hs.Add(curId,temOrders);
}
Session["orders"] = hs;