我怎么能。在LINQ中包含多个级别？

Question

I have the following classes:

public class Problem : AuditableTable
{
    public Problem()
    {
        this.Questions = new List<Question>();
    }
    public int ProblemId { get; set; }
    public string Title { get; set; }
    public virtual ICollection<Question> Questions { get; set; }
}

public Question()
    {
        this.Answers = new List<Answer>();
    }
    public int QuestionId { get; set; }
    public int ProblemId { get; set; }
    public virtual ICollection<Answer> Answers { get; set; }
    public virtual Problem Problem { get; set; }
}
public class Answer : AuditableTable
{
    public int AnswerId { get; set; }
    public int QuestionId { get; set; }
    public string Text { get; set; }
    public virtual Question Question { get; set; }
}

I want to issue a query like this:

        var problems = _problemsRepository.GetAll()
            .Where(p => p.ProblemId == problemId)
            .Include(p => p.Questions)
            .Include(p => p.Questions.Answers)
            .ToList();
        return problems;

So I can see Problem, Question and Answer information. But there is a problem with my last include and I cannot work out how to get the Answers included.

Can someone give me some advice on this.

Answer 1

This is changed in EntityFramework 7.0.

The new syntax would take the form

var problems = _problemsRepository.GetAll()
            .Where(p => p.ProblemId == problemId)
            .Include(p => p.Questions)
            .ThenInclude(q => q.Answers)
            .ToList();

Answer 2

You can use .Select().

var problems = _problemsRepository.GetAll()
            .Where(p => p.ProblemId == problemId)
            .Include(p => p.Questions.Select(q => q.Answers))
            .ToList();

Now your answers will be included.