public ViewResult Checkout(Cart cart, ShippingDetails shippingDetails)
 {
     if (cart.CartLines.Count() == 0)
     {
         ModelState.AddModelError("", "Sorry, your cart is empty");
     }
     if (ModelState.IsValid)
     {
         orderProcessor.ProceesOrder(cart, shippingDetails);
         cart.Clear();
         return(View("Completed"));
     }
     else
     {
         return(View(shippingDetails));
     }
 }