List 增删该查

public class CartItem {
public int proid { get; set; }
public string proname { get; set; }
public int num { get; set; }

}

List<CartItem> list = new List<CartItem>();
//添加功能
for (var i = 0; i < 10;i++ )
list.Add(new CartItem()
{
proid =i,
proname="产品XX"+i,
num=3
});
//添加结束

Response.Write("===========修改后=============");
Response.Write("<br/>");
//修改产品ID为3的购物数量为880
list.ForEach(t => { if (t.proid == 3)t.num = 800; });
list.ForEach(x =>
{
Response.Write(x.proid + " " + x.proname + " " + x.num);
Response.Write("<br/>");
});

list.ForEach(t => { if (t.proid == 4)list.Remove(t); });

Response.Write("===========删除后=============");
Response.Write("<br/>");
list.ForEach(x =>
{
Response.Write(x.proid + " " + x.proname + " " + x.num);
Response.Write("<br/>");
});

Response.Write("===========存在则更新数量后=============");
Response.Write("<br/>");
var newlist = list.Where(t => t.proid == 99).ToList();
if (newlist.Count > 0) list.ForEach(t => { if (t.proid == 99)t.num = t.num + 1; });
else list.Add(new CartItem() {
proid=99,
proname="新增加的名称",
num=1
});

list.ForEach(x =>
{
Response.Write(x.proid + " " + x.proname + " " + x.num);
Response.Write("<br/>");
});