Retrieve Id_product From A Datalist

 Hi all, I'm trig to create a simple cart in ASP.NET/C#. I've create a table named cart in which there are 2 field (user_id and id_product). In my page product I show all product and the cart icon (this is made by an asp.net image_button). When a person click on the cart there's and event in .cs which should insert the relative product in cart table. But how a can retrieve the product id?
This is my .cs page:
 
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

public partial class provacarrello : System.Web.UI.Page
{
    private string connectionString = WebConfigurationManager.ConnectionStrings["MySQLconnection"].ConnectionString;

    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void ImageButton1_Click(object sender, ImageClickEventArgs e)
    {
        MembershipUser mu = Membership.GetUser(User.Identity.Name);
        Guid myGuid = (Guid)mu.ProviderUserKey;

        string insertSQL = "INSERT INTO cart (";
        insertSQL += "userid, id_product)";
        insertSQL += "VALUES(";
        insertSQL += "@userid, @id_product)";

        SqlConnection myConnection = new SqlConnection(connectionString);
        SqlCommand cmd = new SqlCommand(insertSQL, myConnection);

        //Add the parameters
        cmd.Parameters.AddWithValue("@userid", myGuid);
        cmd.Parameters.AddWithValue("@id_product", DataList1.???       <--- ???
    }
}
 
Thank u in advance!