多个分组 linq 嵌套 DTO 不能很好地翻译

Question

这是一个 .NET Core Web API 任务方法。我有一张需要将其转换为嵌套 DTO 的平面表。第一个 DTO 有效，但我似乎无法在分组后让第二个 DTO 嵌套。

我知道我已经正确完成了分组。我只是不确定 DTO 的第二级嵌套是否正确，它抱怨无法转换为某种类型。 LINQ Query to put data in a nested object

有人能指出我正确的方向吗？

 public async Task<List<PointCardViewModel>> GetPointCards()        {
        var data = (from s in db.Students
                    join dc in db.DailyCards on s.StudentId equals dc.StudentId
                    join dcli in db.DailyCardLineItems on dc.CardId equals dcli.CardId
                    join dcob in db.DailyCardOtherBehaviors on dc.CardId equals dcob.CardId
                    select new
                    {
                        s.StudentName,
                        s.StudentGrade,
                        dc.CardId,
                        dc.CardDate,
                        dcli.ClassParticipationPoints,
                        dcli.AssignmentCompletionPoints,
                        dcli.BonusHomeworkPoints,
                        dcli.ClassPeriod,
                        dcob.PersonalAppearancePoints,
                        dcob.LunchPoints,
                        dcob.RecessOtherPoints,
                        dcob.AmHomeroomPoints,
                        dcob.PmHomeroomPoints
                    });

        var queryPointCards = (data
                                 .GroupBy(x => new
                                 {
                                     x.CardId,
                                     x.StudentGrade,
                                     x.StudentName,
                                     x.CardDate,
                                     x.PersonalAppearancePoints,
                                     x.LunchPoints,
                                     x.RecessOtherPoints,
                                     x.AmHomeroomPoints,
                                     x.PmHomeroomPoints
                                 })
                                .Select(x => new PointCardViewModel()
                                {
                                    CardId = x.Key.CardId,
                                    StudentName = x.Key.StudentName,
                                    Grade = x.Key.StudentGrade,
                                    EvaluationDate = x.Key.CardDate,
                                    PersonalAppearancePoints = x.Key.PersonalAppearancePoints,
                                    LunchPoints = x.Key.LunchPoints,
                                    RecessOtherPoints = x.Key.RecessOtherPoints,
                                    AMHomeRoomPoints = x.Key.AmHomeroomPoints,
                                    PMHomeRoomPoints = x.Key.PmHomeroomPoints,

                                    //LineItems = null  --> This works!! But not the below
                                    LineItems = x.Select(c => new LineItemViewModel
                                    {
                                        ClassPeriod = c.ClassPeriod,
                                        BonusHomeworkPoints = c.BonusHomeworkPoints,
                                        ClassParticipationPoints = c.ClassParticipationPoints,
                                        AssignmentCompletionPoints = c.AssignmentCompletionPoints
                                    })
                                }
                              )
                          ).ToListAsync();

        if (db != null)
        {
            return await queryPointCards;
        }
        return null;
    }

Answer 1

您已达到分组限制。摸索后，您无法访问组项目。只允许来自“键”和聚合函数的字段。

所以只需输入data.AsEnumerable() 并在客户端进行分组。