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; }
}
和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 = “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’.
任何想法如何解决这个问题？
解决方法
不支持在Include或IncludeThen中过滤.使用选择创建投影：
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
