CODEWITHSUNDEEP
c#entity-framework
user4144972
user4144972

Reputation: 47

Cast EF DBquery to Viewmodel - Unable to cast object of type 'System.Data.Entity.Infrastructure.DbQuery

I have a Entity Framework query who group the result, I want to pass it to view, but I cant cast it correct to the viewmodel! (I want to show the result in a grid in the view)

If I use this cast

 viewModel.Groupeds = (IEnumerable<Grouped>) result;

I get these error Unable to cast object of type 'System.Data.Entity.Infrastructure.DbQuery1[<>f__AnonymousType42[System.Nullable`1[System.Int32],System.Int32]]' to type

How should I cast it?

public ActionResult Show(int? id)
    {
       IEnumerable<dynamic> result = db.StatData
             .GroupBy(k => new { k.QuestId, k.OptionId })
             .Select(c => new
             {
                 OptionId = c.Select(q => q.OptionId).FirstOrDefault(),
                 Counted = c.Select(q => q.id).Count(),
             });

             var viewModel = new StatsView();
             viewModel.Groupeds = (IEnumerable<Grouped>) result;
    return View(viewModel);
}

public class StatsView
{
    public IEnumerable<Grouped> Groupeds { get; set; }
}


public partial class Grouped
{
    public Nullable<int> Counted { get; set; }
    public Nullable<int> OptionId { get; set; }
}

Upvotes: 2

Views: 4173

Answers (1)

Taher Rahgooy
Taher Rahgooy

Reputation: 6696

The code creates an IEnumerable of anonymous types, you should create IEnumerable of Grouped result. Note that although the anonymous type you created and the Grouped have the same properties, but they are different types and cannot cast them to each other. 

public ActionResult Show(int? id)
{
   //defining result as var is sufficient 
   var result = db.StatData
         .GroupBy(k => new { k.QuestId, k.OptionId })
         .Select(c => new Grouped//<<-here
         {
             OptionId = c.Select(q => q.OptionId).FirstOrDefault(),
             Counted = c.Select(q => q.id).Count(),
         }).ToList();//commit the query
         var viewModel = new StatsView();
         viewModel.Groupeds = result;//No need for casting
   return View(viewModel);
}

It is better to commit the query (i.e by ToList()) before sending it to the view, because if the context disposes, before the view generation, it causes an error.

Upvotes: 2

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