CODEWITHSUNDEEP
asp.net-mvcasp.net-mvc-3linqlinq-to-sqlrepository
Obsivus
Obsivus

Reputation: 8359

LINQ: Why am I getting error on this LINQ Query?

This my method in my repository:

    public List<Question> getallquestion()
    {
        var hej = from Core in db.CoreValue
                    join Question in db.Question on Core.CID equals question.QID
                    join Subject in db.SubjectType on Core.CID equals Subject.SID
                    select new
                    {
                        Core.Cname,
                        Question.QuestionText,
                        Subject.Sname
                    };

        return hej.ToList();

    }

This is the error:

Cannot implicitly convert type 'System.Collections.Generic.List<AnonymousType#1>' to 'NKI3.Models.Question'

What is the solution for this error? I cant seem to find it

My CreateViewModel:

    public class CreateViewModel
    {
        public string QuestionText { get; set; }
        public string Sname { get; set; }
        public string Cname {get;set;}

    }
}

Thanks in Advance!

Best Regards!

Upvotes: 2

Views: 180

Answers (4)

Paul
Paul

Reputation: 12440

Change your select to read like so: 

public List<CreateViewModel> GetAllQuestionViewModel()
    {
        var hej = from Core in db.CoreValue
                    join Question in db.Question on Core.CID equals question.QID
                    join Subject in db.SubjectType on Core.CID equals Subject.SID
                    select new CreateViewModel
                    {
                        Cname = Core.Cname,
                        QuestionText = Question.QuestionText,
                        Sname = Subject.Sname
                    };

        return hej.ToList();

    }

In your controller you would do something like this:

public ActionResult Index() {
    IEnumerable<CreateViewModel> questions = someContext.GetAllQuestionViewModel();
    return View(questions);
}

Upvotes: 1

MarcinJuraszek
MarcinJuraszek

Reputation: 125630

Your linq query produces List of anonymous object (as you use select new { (...) } without any type). You should replace it with select new Question() { (...) }. You should check that select syntax depending on Question class properties.

eg. When you have Name, Text and Subject property is should look like this:

    var hej = from c in db.CoreValue
                join q in db.Question on c.CID equals q.QID
                join s in db.SubjectType on c.CID equals s.SID
                select new Question
                {
                    QID = q.QID,
                    QuestionText  = q.QuestionText
                };

Upvotes: 5

Adrian Iftode
Adrian Iftode

Reputation: 15663

You can't return an anonymous type.


Create a class

public class QuestionResult
{
 public string Core {get; set;}
 public string Question {get; set;}
 public string Subject{get; set;}
}

and use it 

public List<QuestionResult> getallquestion()
    {
        var hej = from Core in db.CoreValue
                    join Question in db.Question on Core.CID equals question.QID
                    join Subject in db.SubjectType on Core.CID equals Subject.SID
                    select new QuestionResult
                    {
                        Core = Core.Cname,
                        Question = Question.QuestionText,
                        Subject = Subject.Sname
                    };

        return hej.ToList();

    }

Upvotes: 0

devdigital
devdigital

Reputation: 34349

Your method is expecting to return a collection of your Question type, but your LINQ query is returning a sequence of an anonymous type. You should change your query, for example changing your projection:

public List<Question> getallquestion()
{
    var hej = from Core in db.CoreValue
                join Question in db.Question on Core.CID equals question.QID
                join Subject in db.SubjectType on Core.CID equals Subject.SID
                select new Question
                {
                    Name = Core.Cname,
                    Text = Question.QuestionText,
                    Subject = Subject.Sname
                };

    return hej.ToList();
}

This is using an object initializer to assign the property values of the Question type from the result of the query. Your property names will differ.

Upvotes: 1

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