protected void RemoveItem_OnClick(object sender, EventArgs e)
        {
            Button      btn  = sender as Button;
            GridViewRow row  = btn.NamingContainer as GridViewRow;
            string      ISBN = CartGridView.DataKeys[row.RowIndex].Values["ISBN"].ToString();

            BookItem myitem = new BookItem
            {
                ISBN     = ISBN,
                quantity = -1
            };

            ServicesShoppingCart.AddItem(myitem);
            RenderGrid();
        }
        protected void AddItemtoCar_OnClick(object sender, EventArgs e)
        {
            Button      btn  = sender as Button;
            GridViewRow row  = btn.NamingContainer as GridViewRow;
            string      ISBN = WishGridView.DataKeys[row.RowIndex].Values["ISBN"].ToString();


            ServicesShoppingCart.AddItem(new BookItem
            {
                ISBN     = ISBN,
                quantity = 1
            });
            ServicesShoppingCart.RemoveWishItem(ISBN);
            RenderGrid();
        }
        protected void AddButton_OnClick(object sender, EventArgs e)
        {
            Button      btn    = sender as Button;
            GridViewRow row    = btn.NamingContainer as GridViewRow;
            string      ISBN   = BookDetailsGridView.DataKeys[row.RowIndex].Values["ISBN"].ToString();
            string      title  = BookDetailsGridView.DataKeys[row.RowIndex].Values["title"].ToString();
            double      price  = double.Parse(BookDetailsGridView.DataKeys[row.RowIndex].Values["price"].ToString());
            BookItem    myitem = new BookItem
            {
                ISBN     = ISBN,
                quantity = 1,
                title    = title,
                price    = price
            };

            ServicesShoppingCart.AddItem(myitem);
            Response.Redirect("Shopping_Cart.aspx");
        }