Question

I’m using ASP.NET MVC 3 with Entity Framework CodeFirst

I have two classes as follows:

Question:

public class Question
{
    public int ID { get; set; }
    public Target Target { get; set; }
    public string QuestionText { get; set; }
    public Category Category { get; set; }
    public QuestionType QuestionType { get; set; }
    public virtual ICollection<Answer> Answers { get; set; }
    public Unit Unit { get; set; }
}

Answer:

public class Answer
{
    public int ID { get; set; }
    public virtual Question Question { get; set; }
    public string AnswerText { get; set; }
    public int Value { get; set; }
}

I also have this ViewModel:

public class QuestionViewModel
{
    public int ID { get; set; }
    public string Question { get; set; }
    public string QuestionType { get; set; }
    public string Target { get; set; }
    public string Category { get; set; }
    public string Unit { get; set; }
    public List<Answer> Answers { get; set; }
}

I want to query the questions table and include the answers, if there are any.

I’ve been trying this style

        var question = (from q in hontgen.Questions
                        where q.ID == id
                        join qt in db.QuestionTypes on q.QuestionType equals qt
                        join t in db.Targets on q.Target equals t
                        join c in db.Categories on q.Category equals c
                        join u in db.Units on q.Unit equals u
                        join a in db.Answers on q.Answers equals a

                        select new QuestionViewModel() {
                            ID = q.ID,
                            Question = q.QuestionText,
                            QuestionType = qt.Type,
                            Category = c.CategoryName,
                            Unit = u.UnitName,
                            Target = t.TargetName,
                            Answers = a
                        }).Single();

But this of course doesn’t roll, because a isn’t a list of answers, but only one answer.

How do I rewrite the query to take all answers in the collection, or all answers with the correct question in “Question”, while at the same time accepting an empty answers-list?

Answer 1

What about a sub query like the following

public class DataRepository
{
    public List<Question> Questions { get; set; }
    public IEnumerable<Answer> Answers { get; set; }

}


public class QandA
{

    DataRepository dr = new DataRepository();

    public void QueryQuestion(int id)
    {
        var question = (from q in dr.Questions
                        where q.ID == id

                        select new QuestionViewModel()
                        {
                            ID = q.ID,
                            Question = q.QuestionText,
                            Answers = (from a in dr.Answers 
                                        where a.Question == q
                                        select a)
                        });
    }

}

}