方法'；跳过'；仅支持LINQ to Entities中的排序输入.方法'；订购人'；必须在方法

我有上面的错误，这很奇怪，因为我没有使用任何"Skip"方法。

我还注意到，switch语句中的sortOrder为null。

你能帮我找出造成这个错误的原因吗？

我的代码：

public ActionResult Index(string sortOrder, string currentFilter, string searchString, int? page)
        {
 ViewBag.CurrentSort = sortOrder;
            ViewBag.BookingIdSortParm = String.IsNullOrEmpty(sortOrder) ? "RecordId" : "";
            ViewBag.ItemSortParm = String.IsNullOrEmpty(sortOrder) ? "Cart" : "";
            ViewBag.UserFullNameSortParm = String.IsNullOrEmpty(sortOrder) ? "UserFullName" : "";
            ViewBag.StatusCodeSortParm = String.IsNullOrEmpty(sortOrder) ? "StatusCode" : "";
            ViewBag.RequestDateSortParm = String.IsNullOrEmpty(sortOrder) ? "RequestDate" : "";
            ViewBag.StartDateSortParm = String.IsNullOrEmpty(sortOrder) ? "StartDate" : "";
            ViewBag.EndDateSortParm = String.IsNullOrEmpty(sortOrder) ? "EndDate" : "";
            if (searchString != null)
            {
                page = 1;
            }
            else
            {
                searchString = currentFilter;
            }
            ViewBag.CurrentFilter = searchString;
            var myBookingList = (from s in SystemDB.Users                              
                                where s.UserLogin == strLoginName
                                join b in SystemDB.Carts on s.DepartmentId equals b.Booking.Item.DepartmentId 
                                where b.Stage != 1 && b.Stage != 5                              
                                orderby b.RecordId descending
                                select b).GroupBy(b => b.CartId).Select(y => y.FirstOrDefault());

            if (!String.IsNullOrEmpty(searchString))
            {

                myBookingList = myBookingList.Where(s => s.RecordId.ToString().Contains(searchString.ToUpper())
                                       || s.CartId.ToUpper().Contains(searchString.ToUpper())
                                       || s.Booking.UserFullName.ToUpper().Contains(searchString.ToUpper())
                                       || s.StatusCode.StatusCodeName.ToUpper().Contains(searchString.ToUpper())
                                       || s.Booking.RequestDate.ToString().Contains(searchString.ToUpper())
                                       || s.Booking.StartDate.ToString().Contains(searchString.ToUpper())
                                       || s.Booking.EndDate.ToString().Contains(searchString.ToUpper()));
            }
            switch (sortOrder)
            {
                case "BookingId":
                    myBookingList = myBookingList.OrderByDescending(s => s.RecordId);
                    break;
                case "Cart":
                    myBookingList = myBookingList.OrderBy(s => s.CartId);
                    break;
                case "UserFullName":
                    myBookingList = myBookingList.OrderBy(s => s.Booking.UserFullName);
                    break;
                case "StatusCode":
                    myBookingList = myBookingList.OrderBy(s => s.StatusCode.StatusCodeName);
                    break;
                case "RequestDate":
                    myBookingList = myBookingList.OrderByDescending(s => s.Booking.RequestDate);
                    break;
                case "StartDate":
                    myBookingList = myBookingList.OrderByDescending(s => s.Booking.StartDate);
                    break;
                case "EndDate":
                    myBookingList = myBookingList.OrderByDescending(s => s.Booking.EndDate);
                    break;
                //default:
                //    throw new ArgumentException("Bad sort order specified", "sortOrder");
            }
            int pageSize = 5;
            int pageNumber = (page ?? 1);

            return View(myBookingList.ToPagedList(pageNumber, pageSize));
}

//default:
//    throw new ArgumentException("Bad sort order specified", "sortOrder");

default:
myBookingList = myBookingList.OrderByDescending(s => s.RecordId);
break;