asp Repeater help required

this is my shoppingcart.aspx page code.....
<%@ Page Title="" Language="C#" MasterPageFile="~/Site.Master" AutoEventWireup="true"
    CodeBehind="ShoppingCart.aspx.cs" Inherits="SessionShoppingCart.ShoppingCart" %>

<asp:Content ID="Content1" ContentPlaceHolderID="HeadContent" runat="server">

<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">
    <asp:Repeater runat="server" ID="rptCategories" DataSourceID="CategoriesData" OnItemCommand="rptCategories_ItemCommand">

            <asp:Button CssClass="fah" ID="Button1" runat="server" Text='<%# Eval("CategoryName") %>'
                CommandArgument='<%# Eval("CategoryID") %>' />


    <asp:SqlDataSource ID="CategoriesData" runat="server" ConnectionString="<%$ ConnectionStrings:NorthwindConnectionString %>"
        SelectCommand="SELECT [CategoryID], [CategoryName] FROM [Categories]">
    <asp:Repeater runat="server" ID="Repeater1" DataSourceID="ProductsData" OnItemCommand="Repeater1_ItemCommand">

            <asp:Button CssClass="waj" ID="Button1" runat="server" Text='<%# Eval("ProductName") %>'
                CommandArgument='<%# Eval("ProductID") %>' />



    <asp:Button ID="Checkout" runat="server" Text="Check Out" OnClick="Checkout_Click" />
    <asp:SqlDataSource ID="ProductsData" runat="server" ConnectionString="<%$ ConnectionStrings:NorthwindConnectionString %>"
        SelectCommand="SELECT Products.ProductID, Products.ProductName, Categories.CategoryName,
        Products.UnitPrice FROM Products INNER JOIN Categories ON Products.CategoryID = Categories.CategoryID
        WHERE Products.CategoryID = @CategoryID">
        <SelectParameters>
            <asp:QueryStringParameter Name="CategoryID" QueryStringField="CategoryID" />
        </SelectParameters>




Here I want to put an item into cart when I click on it...


Now this is code behide page.....

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace SessionShoppingCart
{
    public partial class ShoppingCart : System.Web.UI.Page
    {
        Decimal cost;
        protected void Page_Load(object sender, EventArgs e)
        {
        }

        protected void Basket_RowCreated(object sender, GridViewRowEventArgs e)
        {
            if (e.Row.RowType == DataControlRowType.Footer)
            {
                Literal total = (Literal)e.Row.FindControl("TotalPrice");
                total.Text = cost.ToString("c");
            }
        }
     //   protected void AddToCart_Click(object sender, EventArgs e)
     //   {
     //       var selectedProducts = Products.Rows.Cast<GridViewRow>()
     //.Where(row => ((CheckBox)row.FindControl("SelectedProducts")).Checked)
     //.Select(row => Products.DataKeys[row.RowIndex].Value.ToString()).ToList();
     //       if (Session["Cart"] == null)
     //       {
     //           Session["Cart"] = selectedProducts;
     //       }
     //       else
     //       {
     //           var cart = (List<string>)Session["Cart"];
     //           foreach (var product in selectedProducts)
     //               cart.Add(product);
     //           Session["Cart"] = cart;
     //       }
     //       foreach (GridViewRow row in Products.Rows)
     //       {
     //           CheckBox cb = (CheckBox)row.FindControl("SelectedProducts");
     //           if (cb.Checked)
     //               cb.Checked = false;
     //       }
     //   }
        protected void Checkout_Click(object sender, EventArgs e)
        {
            if (Session["Cart"] != null)
                Response.Redirect("Checkout.aspx");
        }
        protected void Products_SelectedIndexChanged(object sender, EventArgs e)
        {
        }
        protected void Categories_SelectedIndexChanged(object sender, EventArgs e)
        {
            
        }
        protected void rptCategories_ItemCommand(object source, RepeaterCommandEventArgs e)
        {
            Response.Redirect("~/ShoppingCart.aspx?CategoryID=" + e.CommandArgument);
        }
        protected void Repeater1_ItemCommand(object source, RepeaterCommandEventArgs e)
        {
            
            
        }
        
    }
}

<%@ Page Title="" Language="C#" MasterPageFile="~/Site.Master" AutoEventWireup="true"
    CodeBehind="Checkout.aspx.cs" Inherits="SessionShoppingCart.Checkout" %>

<asp:Content ID="Content1" ContentPlaceHolderID="HeadContent" runat="server">
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">

    <asp:GridView ID="Basket" runat="server" AutoGenerateColumns="False" GridLines="None"
        EnableViewState="False" ShowFooter="True" DataKeyNames="ProductID" OnRowCreated="Basket_RowCreated">
        <Columns>
            <asp:TemplateField HeaderText="Remove">
                <ItemTemplate>
                    <asp:CheckBox ID="RemovedProducts" runat="server" />
                </ItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="Product" SortExpression="ProductName">
                <ItemTemplate>
                    <asp:Label ID="ProductName" runat="server" Text='<%# Eval("ProductName") %>' />
                </ItemTemplate>
                <FooterTemplate>
                    <strong>Total Price: </strong>
                </FooterTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="Price" SortExpression="UnitPrice">
                <ItemTemplate>
                    <asp:Label ID="UnitPrice" runat="server" Text='<%# Eval("UnitPrice", "{0:c}") %>' />
                </ItemTemplate>
                <FooterTemplate>
                    <strong>
                        <asp:Literal ID="TotalPrice" runat="server" />
                    </strong>
                </FooterTemplate>
            </asp:TemplateField>
        </Columns>
    </asp:GridView>
    <asp:Button ID="RemoveProduct" runat="server" Text="Remove From Basket" OnClick="RemoveProduct_Click" />
    &nbsp;&nbsp;&nbsp;&nbsp;
    <asp:Button ID="ConfirmPurchase" runat="server" Text="Confirm Purchase" />
    <asp:SqlDataSource ID="BasketData" runat="server"
    ConnectionString="<%$ ConnectionStrings:NorthwindConnectionString %>">
    </asp:SqlDataSource>
</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;
namespace SessionShoppingCart
{
    public partial class Checkout : System.Web.UI.Page
    {
        Decimal cost;
        protected void Page_Load(object sender, EventArgs e)
        {
            if (Session["Cart"] == null)
                Response.Redirect("ShoppingCart.aspx");
            BindBasket();
        }
        protected void RemoveProduct_Click(object sender, EventArgs e)
        {
            var cart = (List<string>)Session["Cart"];
            var removedProducts = Basket.Rows.Cast<GridViewRow>()
              .Where(row => ((CheckBox)row.FindControl("RemovedProducts")).Checked)
              .Select(row => Basket.DataKeys[row.RowIndex].Value.ToString()).ToList();
            cart.RemoveAll(removedProducts.Contains);
            BindBasket();
        }
        protected void BindBasket()
        {
            var sql = "SELECT ProductID, ProductName, UnitPrice FROM Products WHERE ProductID IN ({0})";
            var values = (List<string>)Session["Cart"];
            if (values.Count > 0)
            {
                var parms = values.Select((s, i) => "@p" + i.ToString()).ToArray();
                var inclause = string.Join(",", parms);
                BasketData.SelectCommand = string.Format(sql, inclause);
                BasketData.SelectParameters.Clear();
                for (var i = 0; i < parms.Length; i++)
                {
                    BasketData.SelectParameters.Add(parms[i].Replace("@", ""), values[i]);
                }
                DataView view = (DataView)BasketData.Select(DataSourceSelectArguments.Empty);
                var costQuery = view.Cast<DataRowView>().Select(drv => drv.Row.Field<decimal>("UnitPrice"));
                cost = costQuery.Sum();
                Basket.DataSource = view;
                Basket.DataBind();
            }
        }
        protected void Basket_RowCreated(object sender, GridViewRowEventArgs e)
        {
            if (e.Row.RowType == DataControlRowType.Footer)
            {
                Literal total = (Literal)e.Row.FindControl("TotalPrice");
                total.Text = cost.ToString("c");
            }
        }
    }
}