MVC dealing with multiple LINQ Queries in a single View

Question

Now, I realize that this question has been answered before, but I just can't warp my head around it and make it work in my example:

View
should contain 2 foreach loops fx
foreach(var item in Model.ListA)
foreach(var item in Model.ListB)

Model
should contain a class with a LinqDataContext object and two properties: (ListA and ListB)

Controller
should pass the Model through the View.

How would the Model and Controller look to achieve this? Some simple code examples would be really helpful :)

scottm · Accepted Answer · 2011-10-26 18:26:24Z

1

You've got it a bit backward. Your data context should be in the controller (preferably in a layer even lower that the controller uses). You always want your controller responsible for getting/updating data, and populating the model. Then, the model is delivered to the view with everything needed for the presentation of that data.

public class MyModel
{
    public List<ListAEntity> ListA {get;set;}
    public List<ListBEntity> ListB {get;set;}
}


public class HomeController : Controller
{
    private readonly MyDataContext _context = new MyDataContext();

    public ActionResult Index()
    {
        var model = new MyModel()
        {
            ListA = _context.Get<ListAEntity>().ToList(),
            ListB = _context.Get<ListBEntity>().ToList()
        };

        return View(model);
    }
}

edited Oct 26, 2011 at 18:26

answered Oct 26, 2011 at 18:17

scottm

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1 Comment

BjarkeCK Over a year ago

Thank you both! Really helpfull, yah i've bin told a couple of times, sometimes it just irritates me that i can't reuse the queryies when i make them in the Controller!

Yuval Itzchakov · Accepted Answer · 2014-11-21 13:56:28Z

1

Whoa, padding a LinqDataContext to a View smells pretty bad. Why would you do that?

The controller should get all the data that it needs either from said LinqDataContext or from a backend service and then create a simple ViewModel that only contains an IList or IEnumerable.

public class YourViewModel 
{
    public List<A> ListA {get; set;}
    public List<B> ListB {get; set;}
}

public ActionResult YourControllerAction()
{
   var context = yourDataContext;

   var model = new YourViewModel
   {
      ListA = context.TableA.Where(x => x.Something)
                     .Select(x => x.ConvertSqlToBusinessObject()).ToList(),
      ListB = context.TableB.Where(x => x.Something)
                     .Select(x => x.ConvertSqlToBusinessObject()).ToList()
   };

   return View("Index",model);
}

edited Nov 21, 2014 at 13:56

Yuval Itzchakov

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answered Oct 26, 2011 at 18:17

Michael Stum

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3 Comments

BjarkeCK Over a year ago

Thank you that is brilliant, will look closer! How else am i going to loop through two tables from one view? I could do [[ViewData["linq"] = from c in d... ]] but that wont give me intellesence

BjarkeCK Over a year ago

How would it look if i where not to use lambda expressions? i dont know how they work yet so i would raither user what i know!

Michael Stum Over a year ago

@user scottm essentially has a solution that doesn't use lambda.

Heather · Accepted Answer · 2013-01-02 18:29:17Z

I would add a small addition to the previous answers: The controller should implement the logic necessary to select the proper view and view model, however it should NOT populate the View Model. The view model is perfectly capable of populating itself.

This pattern improves the encapsulation of both the controller and view model as well as creating a cleaner demarcation between concerns. Thus, if I steal Michael's code snippet:

In the controller

public ActionResult YourControllerAction(){
   MyDbContext context = new MyDbContext();
   return View("YourControllerAction", new YourViewModel(context));
}

In the view model

public class YourControllerAction {
    public YourControllerAction(MyDbContext context) {
         ListA = context.TableA.Where(x => x.Something).Select(x => x.ConvertSqlToBusinessObject()).ToList();
         ListB = context.TableB.Where(x => x.Something).Select(x => x.ConvertSqlToBusinessObject()).ToList();
    }
}

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