如何向ThenInclude添加where子句

Question

我有3个实体:

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; }
}

并且Answer.cs:

public class Answer
{
    public int Id { get; set; }
    public string UserId { get; set; }
    public string TextAnswer { get; set; }
}

所以我用答案保存了调查问卷,但现在我想找回问题及其答案的过滤问卷.所以我为此写了linq,但它给我一个错误,有什么我做错了吗？这是一个例子:

questionnaire = _context.Questionnaires.Include(qn => qn.Questions)
.ThenInclude(question => question.Answers.Where(a => a.UserId == userId))
.FirstOrDefault(qn => qn.Id == questionnaireId);

而且我得到了

Message ="属性表达式'q => {来自q.Answers中的答案a,其中Equals([a] .UserId,__ userId_0)选择[a]}'无效.表达式应代表属性访问:'t = > t.MyProperty'.

任何想法如何解决这个问题？

Answer 1

过滤Include或IncludeThen不受支持.使用Select以下方法创建投影

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);

关于这个问题有一个github问题:https://github.com/aspnet/EntityFramework/issues/3474