How to add where clause to ThenInclude

Question

I have 3 entities:

Questionnaire.cs:

public class Questionnaire
{
    public int Id { get; set; }
    public string Name { get; set; }
          


        

Answer 1

You can have navigation properties filtered on memory:

var questionnaire= _context.Questionnaire.FirstOrDefault(qn => qn.Id == questionnaireId);

questionnaire.Answers = _context.Entry(questionnaire)
 .Collection(b => b.Answers )
 .Query()
 .Where(a => a.UserId == userId).ToList();