Passing model data to view in MVC 5

Question

I am darned new to the world of MVC 5 .NET... I am trying to get my head around the Tree Control from Ignite UI.

I need to retrieve my data from my model and pass it to my view... However, I keep getting the following error:

The model item passed into the dictionary is of type 'System.Data.Entity.Infrastructure.DbQuery 1[System.String]', but this dictionary requires a model item of type 'System.Linq.IQueryable 1[DataViewer.Models.Viewer]'.

Here is my model:

namespace DataViewer.Models
{
    [Table("dbo.table")]
    public class Viewer
    {
        [Key, Column(Order=0)] public long id { get; set; }
        public int Revision { get; set; }
        public string GeoPSRType { get; set; }
        public string GeoName { get; set; } 
        public string L2Name { get; set; }  
        public string L3Name { get; set; }
    }
}

etc.

And my Controller:

namespace DataViewer.Controllers
{
    public class ViewerController : Controller
    {
        private ViewerDBContext db = new ViewerDBContext();

        public ActionResult Index()
        {
            var result = db.Items.Select(i => i.GeoName).Distinct().OrderBy(n => n);

            return View(result);
        }
    }
}

And my view:

@model IQueryable<DataViewer.Models.Viewer>

@using Infragistics.Web.Mvc

@(Html.Infragistics().Tree()
        .DataSource(Model)
        .Bindings(b =>
            b.TextKey("GeoName")
            .PrimaryKey("ID")
            .ValueKey("ID")
            .ChildDataProperty("L2PSRType")
            )
        )
        .DataSource(Model)
        .LoadOnDemand(true)
        .DataSourceUrl(Url.Action("tree-data-on-demand"))
        .DataBind()
        .Render()
)

I figured the issue was that I should be passing a strongly typed return-type by using

IQueryable<Viewer> result = 
db.Items.Select(i => i.GeoName).Distinct().OrderBy(n => n);

but that throws a different error:

InvalidOperationException: The model item passed into the dictionary is of type 
'System.Data.Entity.Infrastructure.DbQuery`1[System.String]', 
but this dictionary requires a model item of type 
'System.Linq.IQueryable<DataViewer.Models.Viewer>.' 
An explicit conversion exists, are you missing a cast?

Is this relating to the fact that I'm pretty rusty on strongly typed syntax, or am I just being a total maroon (or is it a combination)?

PS Also, I have no doubt that the Infragistics().Tree() portion of the view is not correct, I am really more concerned about getting my data to my view (at this point). I just wanted to include all code I had...

Answer 1

The problem is the view is expecting different data than you're providing it with your controller.

Inside your view:

@model IQueryable<DataViewer.Models.Viewer>

means the view is expecting an IQueryable<> collection of Viewer's, but inside your controller:

// GET: /Viewer/
public ActionResult Index()
{
    var result = db.Items.Select(i => i.GeoName).Distinct().OrderBy(n => n);

    return View(result);
}

You are passing a collection of strings.

You need to either return Viewer's, or change the model of the view.

Answer 2

You're passing the wrong type to your view. Look at the type of model the view expects:

@model IQueryable<DataViewer.Models.Viewer>

A queryable collection of Viewer objects. But look at what you're giving it:

db.Items.Select(i => i.GeoName).Distinct().OrderBy(n => n);

A collection of GeoName properties. Is GeoName by any chance a string ? (The error implies that it is.)

If your model is expecting a collection of objects, you need to give it such a collection. You can't just give it some strings and expect it to convert those strings into objects.

Answer 3

Change your Action Result to this...

public ActionResult Index()
    {
                    //  var result = db.Items.Select(i => i.GeoName).Distinct().OrderBy(n => n);
         Viewer model = new Viewer();
         model = (from x in db.Items
                 select new Viewer
                 {
                   GeoPSRType = x.FieldName
                  }).Distinct().FirstOrDefault().OrderBy(x => x.SomeField);


        return View(model);
    }

There's probably some syntax errors in that query but this gives you a general understanding of what you need to pass into the View