some problem that i cannot click another page

The error is like that, now i cant click another page, when i click it, it said that
System.NullReferenceException: Object reference not set to an instance of an object.
i think this code line got some problem
var selectedRow = (GridViewRow) ((e.CommandSource as Button).NamingContainer);
so someone can help me to solve this problem?


public partial class imageRetrieve1 : System.Web.UI.Page
{
    DataTable Cart;
    DataView CartView;


    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
            //bindGridView();
            CeilingLight(sender, e);


        if (Session["shoppingSession"] == null)
     &n ...