Question

我的linq查询

   model.Questions = db.Questions
                     .Where (x => x.CategoriesID == categoryId)
                     .Include (qc => qc.QuestionCounters.Where(x => x.MemberID == User.Identity.GetUserId()))
                     .Include (qf => qf.QuestionFavorites.Where(x => x.MemberId == User.Identity.GetUserId()))
                     .Include (qt => qt.QuestionTags)
                     .ToList();

产生错误

＆＃39; Include路径表达式必须引用导航属性在类型上定义。使用虚线路径进行参考导航属性和集合导航的Select运算符属性＆＃39;

任何想法为什么会发生这种情况？

Answer 1

有些人评论说，你不能在Include中使用Where方法。

免责声明：我是该项目的所有者Entity Framework Plus

EF + Query IncludeFilter功能允许过滤相关实体。

model.Questions = db.Questions
                 .Where (x => x.CategoriesID == categoryId)
                 .IncludeFiler (qc => qc.QuestionCounters.Where(x => x.MemberID == User.Identity.GetUserId()))
                 .IncludeFiler (qf => qf.QuestionFavorites.Where(x => x.MemberId == User.Identity.GetUserId()))
                 .IncludeFiler (qt => qt.QuestionTags)
                 .ToList();

维基：EF+ Query IncludeFilter

解决方案＃2

另一种技术是使用投影（这是我的图书馆在幕后做的）

bd.Questions
     .Select(q = new {
        Question = q,
        QuestionCounters = q.QuestionCounters.Where(x => x.MemberID == memberId),
        QuestionFavorites = q.QuestionFavorites.Where(x => x.MemberId == memberId),
        QuestionTags = q.QuestionTags
     })
     .ToList()
     .Select(x => x.Question)
     .ToList();

Answer 2

确定。结束

 IQueryable<HomeViewModel> test = db.Questions
                                  .Where(x => x.CategoriesID == categoryId)
                                  .Select(q => q.ToHomeViewModel(User.Identity.GetUserId()));

和

public static HomeViewModel ToHomeViewModel(this Question q, string memberId)
{
    return new HomeViewModel()
    {
        QuestionCounters = q.QuestionCounters.Where(x => x.MemberID == memberId),
        QuestionFavorites = q.QuestionFavorites.Where(x => x.MemberId == memberId),
        QuestionTags = q.QuestionTags
    };
}

毕竟需要include？ ;）

感谢评论@jle

Include路径表达式必须引用在类型上定义的导航属性。

2 个答案: