public ActionResult آدرس_و_پرداخت(FormCollection values)
    {


        var order = new Order() {};

        TryUpdateModel(order);

        int totalcartprice = 0;

        try
        {
            order.Username = User.Identity.Name;
            order.OrderDate = DateTime.Now;
            order.DeliveryStatusID = 1;

            TryUpdateModel(order);

                //Save Order
                db.Orders.Add(order);
                db.SaveChanges(); <===========here i get error

                //Process the order


            //And rest of the code that i havent write here
        }
        catch
        {
            //Invalid - redisplay with errors
            return View(order);
        }
    }