session + List<T> 实现购物车(asp.net mvc)

毕业设计做电子商务网站，结果卡购物车的实现上卡了N久，以下是我的思路：

1.session 用于存储用户名和购物车

2.List <T>用于存储购物车对象

3.Ajax 传值

部分代码：

1. 购物车：

public class Cart(){
public int cartId{get;set;}
public int albumId{get;set;}
public int quantity{get;set;}
}

2. 购物车实现：

public string CartAdd(string albumId,string quantity)
{
if(session["username"]==null)
return RedictToAction("/Home/Login");
int Id = int.Parse(albumId);
int num = int.Parse(quantity);
int cartid=0;
string str = null;
string username = Session["username"].ToString();
tb_cart cart = new tb_cart();
List<tb_cartDetails> shopcar = null;
if (Session["shopcart"] == null)
{
shopcar = new List<tb_cartDetails>();
cartDetail.cartId = cartid;
cartDetail.albumId = Id;
cartDetail.quantity = num;

shopcar.Add(cartDetail);
Session["shopcart"] = shopcar;
}
else {
shopcar = Session["shopcart"] as List<tb_cartDetails>;
for (int i = 0; i<shopcar.Count;i++ ) {
if (shopcar[i].albumId == Id)
{
shopcar[i].quantity = shopcar[i].quantity + num;
Session["shopcart"] = shopcar;
str = "e";

}
}
if (str == "e")
return str;
else {
cartDetail.cartId = cartid;
cartDetail.albumId = Id;
cartDetail.quantity =
shopcar.Add(cartDetail);
Session["shopcart"] = shopcar;
}
}

  return "添加成功";

}

3.Ajax 传值

$("#addCart").click(function () {
if ($("#_username").is(":empty")) {
$("#warningModal").modal();
$("#modal_info").text("您还没登录，登录之后才可以对商品进行添加");//判断用户是否登录
return false
} else {
var jsonData = "{\"albumId\":\"" + $("#_number").text() + "\", \"quantity\":\""+ $("#qunatity").val() + "\"}";//构建json
$.ajax({
type:"post",
dataType: "text",
contentType: "application/json",
url: "/Cart/CartAdd",
data: jsonData,
success: function (data) {
alert(data);
}
});
}
});