Linq within ASP.NET MVC controller syntax

Question

I am very new to ASP.NET MVC so please be kind.

I have a very simple db with three tables Questions, QuestionOptions, Responses.

my pk in Questions is Id and links to questionId in both QuestionOptions and Responses. I also have a field in Questions called pageId, so multiple questions can appear on one page.

I started with this in my controller;

    // GET: /Questions/ViewQuestion/5
    public ActionResult ViewQuestion(int? id)
    {
        if (id == null)
        {
            return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
        }
        Question question = db.Questions.Find(id);
        if (question == null)
        {
            return HttpNotFound();
        }
        return View(question);
    }

And my View returns a single question and options perfectly;

@model Template.Models.Question

@{
    ViewBag.Title = "Details";
}
<div>
    <h4>Question #@Model.questionId</h4>
    <hr />
<h1> @Html.DisplayFor(model => model.question1)</h1>
<ul>
    @foreach (var item in Model.QuestionOptions)
    {
        <li>@Html.DisplayFor(modelItem => item.questionOption1)</li>
    }
</ul>

But now I am trying to create a view that will display all of the questions with the same pageID - and am getting nowhere.

This is my new ActionResult;

        public ActionResult ViewQuestion(int? id)
    {
        var pageId = id;
        var question = from q in db.Questions
                       where q.pageId == pageId
                       orderby q.ranking
                       select new { q.questionId,
                       q.questionType, q.question1}
                       ;

        return View(question.ToList());
    }

And my View;

@model IEnumerable<Template.Models.Question>

@{
    ViewBag.Title = "View question;";
}

<div>
    @foreach (var item in Model) {
    <h4>Question </h4>
    <hr />
    <h1> @Html.DisplayFor(model => item.question1.AsEnumerable())</h1>

    <ul>
        @foreach (var item in Model.QuestionOptions)
        {
            <li>@Html.DisplayFor(modelItem => item.questionOption1)</li>
    }
</ul>
}

But now it does not recognize QuestionOptions as part of the Model anymore, and even if I comment that section out I still get the error The model item passed into the dictionary is of type -- but this dictionary requires a model item of type System.Collections.Generic.IEnumerable

I know somewhere my syntax is terribly wrong, but I have no idea where after searching for 3 days. Please help!

Your first example was return an object of type Question, but your second example is returning an anonymous type. Is this what you intended? You could just change your select to select q — Mashton
– Mashton, Commented Jan 7, 2014 at 13:06

Viper · Accepted Answer · 2014-01-07 14:54:49Z

3

In your view you are expecting this model: @model IEnumerable<Template.Models.Question>

but your model which you will get from your controller method is not of this type because you are returning a list of an anonymous type.

you need to change

var question = from q in db.Questions
               where q.pageId == pageId
               orderby q.ranking
               select new { q.questionId,
                            q.questionType, 
                            q.question1 };

into something like this:

var question = from q in db.Questions
               where q.pageId == pageId
               orderby q.ranking
               select new Template.Models.Question( )
                          { questionId = q.questionId,
                            questionType = q.questionType, 
                            question1 = q.question1 };

// EDIT:

I take another look into your code. In your method ViewQuestion you are returning the question which you get from your linq-query. So i think the Model you are using is not a special ViewModel. Instead you are passing the Edmx-model. You can do that but its not good practice. This query should work for you:

var questions = from q in db.Questions
                where q.pageId == pageId
                orderby q.ranking
                select q;

But you should think about creating your own class of Question where you only specify the values you need on the page and select them accordingly.

// EDIT2:

Just think about what you really need in your view and create a simple class which can hold this information. (This is a super simple case with no validation rules, etc.)

public class QuestionViewModel
{
    public int QuestionId { get; set; }
    public string QuestionType { get; set; }
    public string QuestionText { get; set; }
    // datatypes are only a guess from me, you need to adapt them
}

don't forget to change the type in your view

@model IEnumerable<QuestionViewModel>

edited Jan 7, 2014 at 14:54

answered Jan 7, 2014 at 12:51

Viper

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5 Comments

Alex Over a year ago

I am getting a new error: "The entity or complex type 'ProjectSiteModel.Question' cannot be constructed in a LINQ to Entities query."

Alex Over a year ago

And it still refuses to see Model.QuestionOptions as part of the Question model.. I would like to post the model for question but it is too long to include in a comment.

Viper Over a year ago

It seems that you have different types of the class Question. Try to specify Template.Models.Question instead of ProjectSiteModel.Question

Alex Over a year ago

I believe you have hit on my main problem - there is very little documentation on DB First. I am relying on the edmx. Can you please give me an example of what a viewModel for this scenario would be, please?

Alex Over a year ago

you have really inspired me. I am still having issues with this select, but your instructions made me take a good look at how to create ViewModels. Thanks a lot for helping.

Murali Murugesan · Accepted Answer · 2014-01-07 12:53:29Z

2

You are creating a Anonymous type and not strongly typed which is Template.Models.Question expected by view

Better change this to work for your Model based view

select new { q.questionId,
                       q.questionType, q.question1}

To

select new Template.Models.Question{ q.questionId,
                       q.questionType, q.question1}

answered Jan 7, 2014 at 12:53

Murali Murugesan

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Comments

Alex · Accepted Answer · 2014-01-07 13:08:51Z

I'm not sure I am supposed to do this, but as you've asked to see my Question class and it will not fit in a comment, I post it here. Please forgive me if this is a breech of etiquette.

namespace Template.Models
{
using System;
using System.Collections.Generic;

public partial class Question
{
    public Question()
    {
        this.QuestionOptions = new HashSet<QuestionOption>();
        this.Responses = new HashSet<Response>();
    }

    public int questionId { get; set; }
    public int eventId { get; set; }
    public int pageId { get; set; }
    public string question1 { get; set; }
    public int questionType { get; set; }
    public Nullable<int> linkedTo { get; set; }
    public Nullable<int> options { get; set; }
    public Nullable<int> ranking { get; set; }

    public virtual ICollection<QuestionOption> QuestionOptions { get; set; }
    public virtual QuestionType QuestionType1 { get; set; }
    public virtual ICollection<Response> Responses { get; set; }
    }
}

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