Question

我有一些代码从我的数据库中选择一些值。我有一个IQueryable请求，其中包含ICollection of rooms。

我想要List<ICollection<rooms>>。我尝试了以下内容，我收到了上述错误。

任何想法??

public ActionResult _roomChecker(checkRooms JSONdata){
        var rooms = db.rooms.Include(r=>r.building).Include(r=>r.facilities);
        rooms = rooms.Where(r => r.capacity >= JSONdata.capacity);
        if (JSONdata.type != "Any")
        {
            rooms = rooms.Where(r => r.roomType.Equals(JSONdata.type));
        }
        if (JSONdata.park != "Any")
        {
            rooms = rooms.Where(r => r.building.park.Equals(JSONdata.park));
        }

        if (JSONdata.facilities != null)
        {
            for (var i = 0; i < JSONdata.facilities.Length; i++)
            {
                rooms = rooms.Where(r => r.facilities.Any(f => f.facilityName.Equals(JSONdata.facilities[i])));

            }
        }

        var proposedRequest = db.requests.Include(r => r.rooms);
        proposedRequest = proposedRequest.Where(r=>r.booked.Equals(1));
        proposedRequest = proposedRequest.Where(r => r.roundID.Equals(JSONdata.roundID));
        proposedRequest = proposedRequest.Where(r => r.day.Equals(JSONdata.day));
        proposedRequest = proposedRequest.Where(s => s.start < JSONdata.start + JSONdata.length && s.start + s.length > JSONdata.start);
        int[] standardWeeks = new int[12] {1,2,3,4,5,6,7,8,9,10,11,12};
        var containsStandard = standardWeeks.Intersect(JSONdata.weeks);
        if (containsStandard.Count()!=0)
        {
            proposedRequest = proposedRequest.Where(r => r.weeks_request.Any(f => JSONdata.weeks.Contains(f.week)) || r.weeks.Equals(1));
        }
        else {
            proposedRequest = proposedRequest.Where(r => r.weeks_request.Any(f => JSONdata.weeks.Contains(f.week)));
        }

    //ERROR OCCURS ON THIS LINE BELOW

        List<ICollection<room>> bookedRooms = proposedRequest.Select(r => r.rooms).ToList();


        var deptRooms = db.rooms.Include(r => r.building).Include(r => r.facilities).Where(r => r.belongsTo.Equals(JSONdata.deptCode));

        roomCheckerObject suitableRooms = new roomCheckerObject();
        suitableRooms.code = JSONdata.deptCode;
        suitableRooms.roomNo = JSONdata.roomNo;
        suitableRooms.RequestNo = JSONdata.RequestNo;
        if(rooms.Count() >0){
            suitableRooms.rooms = rooms.ToList();
            var buildings = rooms.Select(r => r.building).Distinct();
            suitableRooms.buildings = buildings.ToList();
        }
        if(bookedRooms.Count() >0){
            suitableRooms.bookedRooms = bookedRooms;
        }

        if(deptRooms.Count() >0){
            suitableRooms.deptRooms = deptRooms.ToList();
        }
        return PartialView(suitableRooms);}

Answer 1

很难说究竟是什么导致错误，但我可以看到3个可能的罪魁祸首：

1）您正在使用.Equals()与Linq to entities（L2E）查询。这可能会导致问题，请参阅here。

2）您说错误发生在声明List<ICollection<room>>的行上。在这一行中，您在任何L2E语句中首次调用.ToList()。只有现在才能对数据库执行L2E查询（see EF Query Execution），这意味着先前的L2E语句中的任何错误（使用.Equals()）都可能抛出异常。

3）proposedRequest.Select(r => r.rooms).ToList();真的会返回List<ICollection<room>>吗？尝试使用.SelectMany()（虽然这可能会产生不良影响），或者通过完整性检查将List<ICollection<room>>更改为var，以查看查询将返回的内容。

LINQ相关错误“无法创建类型'System.Object'的常量值。在此上下文中仅支持基本类型或枚举类型

1 个答案: