The Include path expression must refer to a navigation property defined on the type.

Question

My linq query

   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();

produces the error

'The Include path expression must refer to a navigation property defined on the type. Use dotted paths for reference navigation properties and the Select operator for collection navigation properties.'

Any ideas why is this happening?

You can't use Include to select data. There are lots of posts on this already. — Equalsk, Aug 03 '17 at 14:19
Duplicate - See this https://stackoverflow.com/questions/15980665/ef-lambda-the-include-path-expression-must-refer-to-a-navigation-property and this https://stackoverflow.com/questions/38676029/the-include-path-expression-must-refer-to-a-navigation-property-defined-on-the-t. — , Aug 03 '17 at 14:21

Jonathan Magnan · Answer 1 · 2018-03-05T12:52:01.737

As some people commented, you cannot use Where method in Include.

Disclaimer: I'm the owner of the project Entity Framework Plus

EF+ Query IncludeFilter feature allow filtering related entities.

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();

Wiki: EF+ Query IncludeFilter

Solution #2

Another technique is by using projection (which is what my library do under the hood)

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();

OrElse · Accepted Answer · 2017-08-03T15:44:09.077

Ok. Ended up with

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

and

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
    };
}

How needs include after all? ;)

Thanks for commenting @jle

The Include path expression must refer to a navigation property defined on the type.

2 Answers2