protected void GridView3_RowCommand(object sender, GridViewCommandEventArgs e)
        {
            if (sessionCust != null)
            {
                sessionCart = new Cart(sessionCust.CustomerID, 1);
                //Get the button clicked.
                Button btnAddToCart = ((Button)e.CommandSource);
                //get the row the button lives in
                GridViewRow currentRow = ((GridViewRow)btnAddToCart.NamingContainer);
                //find the quantity text box
                TextBox txtQuantity = ((TextBox)currentRow.FindControl("txtQuantity"));
                Int32 qty = Convert.ToInt32(txtQuantity.Text);
                //get the row's datakey value by keyname using .Values["keyname"] or if you only have one datakey field you can just use .Value
                Int32 prodId = Convert.ToInt32(GridView3.DataKeys[currentRow.RowIndex].Values["ProductID"].ToString());
                //pass the quantity value and the prodid to your AddToCart method.
                //CartFunctions.AddItemToCart(prodId, txtQuantity.Text, 0.0M);

                sessionCart.AddToCart(prodId, qty);
                //Response.Write for testing only..
                lblAddToCart.Text = txtQuantity.Text + " of ProductID " + prodId + " added to cart.";
            }
            else
                Response.Write("Error: no customer is in session.");
        }