I have 3 entities:
Questionnaire.cs
:
public class Questionnaire
{
public int Id { get; set; }
public string Name { get; set; }
public ICollection<Question> Questions { get; set; }
}
Question.cs
:
public class Question
{
public int Id { get; set; }
public string Text { get; set; }
public ICollection<Answer> Answers { get; set; }
}
and Answer.cs
:
public class Answer
{
public int Id { get; set; }
public string UserId { get; set; }
public string TextAnswer { get; set; }
}
So I saved the questionnaire with answers but now i want to retrieve filtered questionnaire with questions and its answers. So i wrote linq for that, but it throws me an error, is there anything i do wrong? here is the example:
questionnaire = _context.Questionnaires.Include(qn => qn.Questions)
.ThenInclude(question => question.Answers.Where(a => a.UserId == userId))
.FirstOrDefault(qn => qn.Id == questionnaireId);
And i am getting
Message = "The property expression 'q => {from Answer a in q.Answers where Equals([a].UserId, __userId_0) select [a]}' is not valid. The expression should represent a property access: 't => t.MyProperty'.
Any ideas how to solve this problem?
Filtering in Include
or IncludeThen
is not supported. Create projection by using Select
:
questionnaire = _context.Questionnaires
.Select(n => new Questionnaire
{
Id = n.Id,
Name = n.Name,
Questions = n.Questions.Select(q => new Question
{
Id = q.Id,
Text = q.Text,
Answers = q.Where(a => a.UserId == userId).ToList()
}).ToList()
})
.FirstOrDefault(qn => qn.Id == questionnaireId);
There is a github issue about this problem: https://github.com/aspnet/EntityFramework/issues/3474