System.InvalidCastException：'无法将类型为'Food_Founder.Models.OrderDetail'的对象转换为类型为'System.IConvertible'。

Question

正如标题所述，我最近遇到了这个问题，对此我感到困惑。该错误如何发生，为什么？我已经正确编写了代码，似乎没有问题。在研究了此类错误之后，我仍然不明白。

        public ActionResult AddOrder(OrderDetail orderDetail)
        {
            string message = "";
            if (ModelState.IsValid)
            {
                using (myDatabaseEntities1 myDatabase1 = new myDatabaseEntities1())
                {
                    String userid = Convert.ToString(myDatabase1.OrderDetails.Where(a => a.User_ID == orderDetail.User_ID).FirstOrDefault());
                    userid = User.Identity.GetUserId();
                    DateTime CurrentDT = DateTime.UtcNow;
                    var Date = Convert.ToDateTime(myDatabase1.OrderDetails.Where(a => a.OrderDate == orderDetail.OrderDate).FirstOrDefault());
                    Date = CurrentDT;
                    Double T_Price = Convert.ToDouble(myDatabase1.OrderDetails.Where(a => a.OrderPrice == orderDetail.OrderPrice).FirstOrDefault());

                    //WF
                    var A_ChickenChop_BP = myDatabase1.OrderDetails.Where(a => a.A_ChickenChop_BP == orderDetail.A_ChickenChop_BP).FirstOrDefault();
                    var A_ChickenChop_M = myDatabase1.OrderDetails.Where(a => a.A_ChickenChop_M == orderDetail.A_ChickenChop_M).FirstOrDefault();
                    var A_Spaghetti_AH = myDatabase1.OrderDetails.Where(a => a.A_Spaghetti_AH == orderDetail.A_Spaghetti_AH).FirstOrDefault();
                    var A_Spaghetti_P = myDatabase1.OrderDetails.Where(a => a.A_Spaghetti_P == orderDetail.A_Spaghetti_P).FirstOrDefault();
                    var A_Spaghetti_S = myDatabase1.OrderDetails.Where(a => a.A_Spaghetti_S == orderDetail.A_Spaghetti_S).FirstOrDefault();
                    //CF
                    var A_ChickenRice_CB = myDatabase1.OrderDetails.Where(a => a.A_ChickenRice_CB == orderDetail.A_ChickenRice_CB).FirstOrDefault();
                    var A_ChickenRice_CW = myDatabase1.OrderDetails.Where(a => a.A_ChickenRice_CW == orderDetail.A_ChickenRice_CW).FirstOrDefault();
                    var A_ChickenRice_D = myDatabase1.OrderDetails.Where(a => a.A_ChickenRice_D == orderDetail.A_ChickenRice_D).FirstOrDefault();
                    var A_WantanMee_NS = myDatabase1.OrderDetails.Where(a => a.A_WantanMee_NS == orderDetail.A_WantanMee_NS).FirstOrDefault();
                    var A_WantanMee_IS = myDatabase1.OrderDetails.Where(a => a.A_WantanMee_IS == orderDetail.A_WantanMee_IS).FirstOrDefault();

                    //WF
                    Double PriceOfF1 = Convert.ToDouble(A_ChickenChop_BP) * 14.9;
                    Double PriceOfF2 = Convert.ToDouble(A_ChickenChop_M) * 14.9;
                    Double PriceOfF3 = Convert.ToDouble(A_Spaghetti_AH) * 10.9;
                    Double PriceOfF4 = Convert.ToDouble(A_Spaghetti_P) * 10.9;
                    Double PriceOfF5 = Convert.ToDouble(A_Spaghetti_S) * 10.9;
                    //CF
                    Double PriceOfF6 = Convert.ToDouble(A_ChickenRice_CB) * 6.9;
                    Double PriceOfF7 = Convert.ToDouble(A_ChickenRice_CW) * 6.9;
                    Double PriceOfF8 = Convert.ToDouble(A_ChickenRice_D) * 6.9;
                    Double PriceOfF9 = Convert.ToDouble(A_WantanMee_NS) * 6.9;
                    Double PriceOfF10 = Convert.ToDouble(A_WantanMee_IS) * 6.9;

                    T_Price = PriceOfF1 + PriceOfF2 + PriceOfF3 + PriceOfF4 + PriceOfF5
                        + PriceOfF6 + PriceOfF7 + PriceOfF8 + PriceOfF9 + PriceOfF10;

                    if (T_Price > 1)
                    {
                        myDatabase1.OrderDetails.Add(orderDetail);
                        myDatabase1.SaveChanges();
                        message = "The order has been placed successfully";
                    }
                    else
                    {
                        message = "Please order any food at least one";
                    }
                }
            }
            ViewBag.Message = message;
            RedirectToAction("Index", "Home");
            return View(orderDetail);
        }

该错误发生在使数据库数据加倍的那一行。如您所见，我做的很多数据都是双倍的，所有这些都解决了这个问题。 顺便说一下，我使数据库中的所有这些数据都是int类型。

        [Display(Name = "Order ID")]
        public int OrderID { get; set; }

        [Display(Name = "User ID")]
        public int User_ID { get; set; }

        [Display(Name = "Order Date")]
        [DataType(DataType.Date)]
        [DisplayFormat(ApplyFormatInEditMode = true, DataFormatString = "{0:dd/MM/yyyy}")]
        public Nullable<System.DateTime> OrderDate { get; set; }

        [Display(Name = "Order Address")]
        [Required(AllowEmptyStrings = false, ErrorMessage = "Address is required for the order")]
        public string OrderAddress { get; set; }

        [Range(0, int.MaxValue, ErrorMessage = "Amount of the food is not valid")]
        [Display(Name = "Amount Of ChickenChop in Black Pepper Sauce")]
        public int A_ChickenChop_BP { get; set; }

        [Range(0, int.MaxValue, ErrorMessage = "Amount of the food is not valid")]
        [Display(Name = "Amount Of ChickenChop in Mushroom Sauce")]
        public int A_ChickenChop_M { get; set; }

        [Range(0, int.MaxValue, ErrorMessage = "Amount of the food is not valid")]
        [Display(Name = "Amount Of Angel Hair Spaghetti")]
        public int A_Spaghetti_AH { get; set; }

        [Range(0, int.MaxValue, ErrorMessage = "Amount of the food is not valid")]
        [Display(Name = "Amount Of Penne Spaghetti")]
        public int A_Spaghetti_P { get; set; }

        [Range(0, int.MaxValue, ErrorMessage = "Amount of the food is not valid")]
        [Display(Name = "Amount Of Shell Spaghetti")]
        public int A_Spaghetti_S { get; set; }

        [Range(0, int.MaxValue, ErrorMessage = "Amount of the food is not valid")]
        [Display(Name = "Amount Of ChickenRice with Chicken Breast part")]
        public int A_ChickenRice_CB { get; set; }

        [Range(0, int.MaxValue, ErrorMessage = "Amount of the food is not valid")]
        [Display(Name = "Amount Of ChickenRice with Chicken Wing part")]
        public int A_ChickenRice_CW { get; set; }

        [Range(0, int.MaxValue, ErrorMessage = "Amount of the food is not valid")]
        [Display(Name = "Amount Of ChickenRice with Drumstick part")]
        public int A_ChickenRice_D { get; set; }

        [Range(0, int.MaxValue, ErrorMessage = "Amount of the food is not valid")]
        [Display(Name = "Amount Of Non-Spicy Wantan Mee")]
        public int A_WantanMee_NS { get; set; }

        [Range(0, int.MaxValue, ErrorMessage = "Amount of the food is not valid")]
        [Display(Name = "Amount Of Spicy Wantan Mee")]
        public int A_WantanMee_IS { get; set; }

        [Display(Name = "Total Price")]
        public Nullable<int> OrderPrice { get; set; }

        [Display(Name = "Is the order paid?")]
        public Nullable<bool> Is_Paid { get; set; }

有人可以向我解释此错误的发生方式和解决方法吗？

遇到此错误的确切行是

                    Double T_Price = Convert.ToDouble(myDatabase1.OrderDetails.Where(a => a.OrderPrice == orderDetail.OrderPrice).FirstOrDefault());

                    //WF
                    var A_ChickenChop_BP = myDatabase1.OrderDetails.Where(a => a.A_ChickenChop_BP == orderDetail.A_ChickenChop_BP).FirstOrDefault();
                    var A_ChickenChop_M = myDatabase1.OrderDetails.Where(a => a.A_ChickenChop_M == orderDetail.A_ChickenChop_M).FirstOrDefault();
                    var A_Spaghetti_AH = myDatabase1.OrderDetails.Where(a => a.A_Spaghetti_AH == orderDetail.A_Spaghetti_AH).FirstOrDefault();
                    var A_Spaghetti_P = myDatabase1.OrderDetails.Where(a => a.A_Spaghetti_P == orderDetail.A_Spaghetti_P).FirstOrDefault();
                    var A_Spaghetti_S = myDatabase1.OrderDetails.Where(a => a.A_Spaghetti_S == orderDetail.A_Spaghetti_S).FirstOrDefault();
                    //CF
                    var A_ChickenRice_CB = myDatabase1.OrderDetails.Where(a => a.A_ChickenRice_CB == orderDetail.A_ChickenRice_CB).FirstOrDefault();
                    var A_ChickenRice_CW = myDatabase1.OrderDetails.Where(a => a.A_ChickenRice_CW == orderDetail.A_ChickenRice_CW).FirstOrDefault();
                    var A_ChickenRice_D = myDatabase1.OrderDetails.Where(a => a.A_ChickenRice_D == orderDetail.A_ChickenRice_D).FirstOrDefault();
                    var A_WantanMee_NS = myDatabase1.OrderDetails.Where(a => a.A_WantanMee_NS == orderDetail.A_WantanMee_NS).FirstOrDefault();
                    var A_WantanMee_IS = myDatabase1.OrderDetails.Where(a => a.A_WantanMee_IS == orderDetail.A_WantanMee_IS).FirstOrDefault();

                    //WF
                    Double PriceOfF1 = Convert.ToDouble(A_ChickenChop_BP) * 14.9;
                    Double PriceOfF2 = Convert.ToDouble(A_ChickenChop_M) * 14.9;
                    Double PriceOfF3 = Convert.ToDouble(A_Spaghetti_AH) * 10.9;
                    Double PriceOfF4 = Convert.ToDouble(A_Spaghetti_P) * 10.9;
                    Double PriceOfF5 = Convert.ToDouble(A_Spaghetti_S) * 10.9;
                    //CF
                    Double PriceOfF6 = Convert.ToDouble(A_ChickenRice_CB) * 6.9;
                    Double PriceOfF7 = Convert.ToDouble(A_ChickenRice_CW) * 6.9;
                    Double PriceOfF8 = Convert.ToDouble(A_ChickenRice_D) * 6.9;
                    Double PriceOfF9 = Convert.ToDouble(A_WantanMee_NS) * 6.9;
                    Double PriceOfF10 = Convert.ToDouble(A_WantanMee_IS) * 6.9;