Entity Framework 6 - Handling loading of nested objects

Question

Here is a simplified version of a class hierarchy I am using with entity framework.

public class Questionnaire
{
   public int Id { get; set; }
   public ICollection<Question> Questions { get; set; }
}

public class Question
{
   public int Id { get; set; }
   public ICollection<Question> ChildQuestions { get; set; }

   // Navigation properties
   public int QuestionnaireId { get; set; }
   public virtual Questionnaire Questionnaire { get; set; }
   public int? ParentQuestionId { get; set; }
   public virtual Question ParentQuestion { get; set; }
}

So a questionnaire has a collection of questions and each question can have its own collection of child questions.

The problem I face is that when I retrieve a questionnaire from the database the collection of questions it holds includes all questions associated with that questionnaire, including ones which are nested within other questions.

The questions themselves correctly contain references to their child questions.

At the moment I'm working around it by removing all Questions from the Questionnaire.Questions collection where ParentQuestionId != null.

Is there a way of telling Entity Framework to only include in Questionnaire.Questions the Questions which have a null ParentQuestionId?

Oliboy50 · Accepted Answer · 2014-07-05 18:47:21Z

3

In your controller :

Questionnaire questionnaire = 
    db.QuestionnaireDBSet
      .Include(x => x.Questions.Where(q => q.ParentQuestionId == null))
      .FirstOrDefault(x => x.Id == id);

Assuming db is your QuestionnaireDBContext...

EDIT : As the OP said, it seems we can't filter using Include. So the answer above would only work in a perfect world. But now you should try something like this instead :

Questionnaire questionnaire = 
    db.QuestionnaireDBSet
      .Include(x => x.Questions)
      .Where(x => x.Questions.Any(q => q.ParentQuestionId == null))
      .FirstOrDefault(x => x.Id == id);

I don't have any test environment so i can only give you some suggestions.

edited Jul 5, 2014 at 18:47

answered Jul 5, 2014 at 16:56

Oliboy50

2,7513 gold badges32 silver badges37 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

phil soady Over a year ago

or should that be != null ?

Oliboy50 Over a year ago

@philsoady "which have a null ParentQuestionId" sayd the OP

Steve Over a year ago

Thanks, but this doesn't work for me. I get the error: The Include path expression must refer to a navigation property defined on the type. Use dotted paths for reference navigation properties and the Select operator for collection navigation properties. Also, I've read that Include does not support filtering, or has it been added in the latest EF version?

Collectives™ on Stack Overflow

Entity Framework 6 - Handling loading of nested objects

1 Answer 1

3 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related