How To Maintain Shopping Cart

<%@ Page Title="" Language="C#" MasterPageFile="~/MasterPage/Main.master" AutoEventWireup="true"
    CodeFile="ShowProduct.aspx.cs" Inherits="Guest_ShowProduct" %>

<asp:Content ID="Content1" ContentPlaceHolderID="head" runat="Server">
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="Server">
    <center>
        <table width="100%">
            <asp:DataList ID="dtlist" runat="server" RepeatColumns="4" RepeatDirection="Horizontal"
                OnItemCommand="dtlist_ItemCommand" OnItemDataBound="dtlist_ItemDataBound">
                <ItemTemplate>
                    <table>
                        <tr>
                            <td>
                                <asp:ImageButton ID="imgPic" runat="server" Height="150px" Width="150px" CommandName="Cart"
                                    ImageUrl='<%# Eval("image") %>' />
                            </td>
                        </tr>
                        <tr>
                            <td>
                                <asp:Label ID="lblid" runat="server" Text='<%# Eval("uniqueid")%>'></asp:Label>
                            </td>
                        </tr>
                        <tr>
                            <td>
                                <asp:Label ID="lblProductName" runat="server" Text='<%# Eval("productName")%>'></asp:Label>
                            </td>
                        </tr>
                        <tr>
                            <td>
                                <asp:Label ID="lblPrice" runat="server" Text='<%#  Eval("Amount") %>'></asp:Label>
                            </td>
                        </tr>
                        <tr>
                            <td>
                                <asp:LinkButton ID="lnkAdd" runat="server" PostBackUrl="~/Guest/AddToCart.aspx">Add To Cart</asp:LinkButton>
                            </td>
                        </tr>
                    </table>
                </ItemTemplate>
            </asp:DataList>
        </table>
    </center>
</asp:Content>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;

public partial class Guest_ShowProduct : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            showproduct();
           
        }

        

    }
    public void showproduct()
    {
        d_ProductDetails d = new d_ProductDetails();
        DataTable dt = new DataTable();
        dt = d.getProduct();
        if (dt != null && dt.Rows.Count > 0)
        {
            dtlist.DataSource = dt;
            dtlist.DataBind();
        }
    }
    public void collectItem()
    {
        DataTable dt = new DataTable();
        dt.Columns.Add("ProductID", typeof(string));
        dt.Columns.Add("ProductName", typeof(string));
        dt.Columns.Add("ProductCost", typeof(string));
        dt.Columns.Add("ProductImage", typeof(string));
        Session["collect"] = dt;

    }

    protected void dtlist_ItemDataBound(object sender, DataListItemEventArgs e)
    {
        
    }
    public void cart()
    { 
    
    }
    protected void dtlist_ItemCommand(object source, DataListCommandEventArgs e)
    {
         DataTable dt = (DataTable)Session["collect"];
        if (e.CommandName == "Cart")
        {
            if (Session["collect"] == null)
            {
                DataRow dr = dt.NewRow();
                DataList rowSelect = (DataList)(((ImageButton)e.CommandSource).NamingContainer);
                Label Product = (Label)rowSelect.FindControl("lblProductName");
                Label price = (Label)rowSelect.FindControl("lblPrice");
                Label id = (Label)rowSelect.FindControl("lblid");
            
                dr["ProductID"] = id.Text;
                dr["ProductCost"] = price.Text;
                dr["ProductName"] = Product.Text;
                
                dt.Rows.Add(dr);

                Session["collect"] = dt;
            }
            else
            {
                var cart = (List<string>)Session["Cart"];
                foreach (var product in cart)
                {
                    cart.Add(product);
                    Session["Cart"] = cart;
                }
            }
        }
    }
}