Question

I have a class

public partial class Advertisement
{
    public int AdvertisementId { get; set; }
    public string Description { get; set; }
    public City CityIdFrom { get; set; }
    public City CityIdTo { get; set; }
    public int Weight { get; set; }
}

which represents the table Advertisements. Same goes for a class City

public class City
{
    public Int32 CityId { get; set; }
    public string Name { get; set; }
}

Now I have a view controller named View1Controller which has

DbConnection db = new DbConnection();

public ActionResult Index()
{
    var query = from item in db.Advertisements.AsEnumerable() select item;

    return View(query);
}

And finally there is a View1.cshtml file

@model IEnumerable<MvcApplication1.Models.Advertisement>

@{
    ViewBag.Title = "View1";
}

<h2>View1</h2>

<table>
@foreach(var item in Model)
{
    <tr>
        <td>@item.Description</td>
        <td>@item.CityIdFrom</td>
    </tr>
}
</table>

I took a look in SQL Profiler and the query generated looked

SELECT 
[Extent1].[AdvertisementId] AS [AdvertisementId], 
[Extent1].[Description] AS [Description], 
[Extent1].[Weight] AS [Weight], 
[Extent1].[CityIdFrom_CityId] AS [CityIdFrom_CityId], 
[Extent1].[CityIdTo_CityId] AS [CityIdTo_CityId]
FROM [dbo].[Advertisements] AS [Extent1]

And executing the query I get:

2   None    5000    1   2
3   Test    1000    3   4

However, when query is hit, both CityIdFrom and CityIdTo are null for some reason. Thus the result table looks

None 
Test 

Instead of expected

None 1
Test 3

What am I doing wrong?

Answer 1

you either need to add an Include for CityFrom and CityTo, or you Can make these referenced entities virtual. Option 1 (Include) avoids the select n+1 issue so commomn among ORMs.

var query = db.Advertisements.Include("CityIdFrom").Include("CityIdTo").AsEnumerable();
return View(query);