ASP.NET null reference to a model

Question

I have two models:

ApplicationUsers: ( The default that comes with Identity framework )

public class ApplicationUser : IdentityUser
{
    public async Task<ClaimsIdentity> GenerateUserIdentityAsync(UserManager<ApplicationUser> manager)
    {
        // Note the authenticationType must match the one defined in CookieAuthenticationOptions.AuthenticationType
        var userIdentity = await manager.CreateIdentityAsync(this, DefaultAuthenticationTypes.ApplicationCookie);
        // Add custom user claims here
        return userIdentity;
    }
}

and Room:

public class Room
{
    public int Id { get; set; }
    public string RoomName { get; set; }
    public ApplicationUser User1 { get; set; }
    public ApplicationUser User2 { get; set; }
    public ApplicationUser User3 { get; set; }
}

I created a new user at AppliactionUser:

And I manually added a new Room and reference to that User:

NOTE: It might not seem from the images, but their ids are the same, I doubled-checked it, the reason it looks different in these pictures is because there's not enough space to display the full length.

But when I ran my web and wrote this code on Home Controller :

public class HomeController : Controller
{
    private ApplicationDbContext db = new ApplicationDbContext();
    public ActionResult Index()
    {
        var varForDebug = db.Rooms.Find(1); // Room id 1

        return View();
    }

and made a breaking point at varForDebug I couldn't see an ApplicationUser at User1:

Why is that and how it could be solved?

Note: I'm using: ASP.NET MVC Web Application (.NET Framework ) 4.6.1 with Identity.

Note2: Include wants only string parameter from some reason, whys that?

Maybe I should consider adding Room property to ApplicationUser?

Either enable lazy loading and make those properties virtual or follow the below answer about calling Include for each relationship you need to load like `Include("propertyname")` — Mat J, Aug 25 '19 at 16:29

David Donari · Answer 1 · 2019-08-25T19:17:46.023

2

First, add the references:

using System.Linq;

and

using System.Data.Entity;

If you want to keep using the Find operation, use:

 var varForDebug = db.Rooms.Find(1); // Room id 1 `

 // Load the user 
 context.Entry(varForDebug).Reference(p => p.User1).Load();

or

db.Rooms.Include(r => r.User1).FirstOrDefault(x=>x.Id==1);

edited Aug 25 '19 at 19:17

answered Aug 25 '19 at 16:37

David Donari

599
7
17

1

Yeah but Include wants only String from some reason, how could it be solved? Edit: Worked by using Include("User1") instead. – Dorki Aug 25 '19 at 16:42
2

@Dorki have you added the reference using **System.Linq;** or **System.Data.Entity;**? – David Donari Aug 25 '19 at 16:49
1

@Dorki I updated the answer. Please check if it improves the response to your question. – David Donari Aug 25 '19 at 19:20

H H · Accepted Answer · 2019-08-25T16:32:29.683

1

Use db.Rooms.Include(r => r.User1).FirstOrDefault(r => r.Id == 1);

and repeat that for User2, User3 etc.

edited Aug 25 '19 at 16:32

answered Aug 25 '19 at 16:26

H H

263,252
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514

1

I tried, tho it says: "Cannot convert lambda expression to type 'String' because it is not delegate type". – Dorki Aug 25 '19 at 16:29
2

Yeah, Include() and Find() don't go together. I just took a gamble. Corrected. – H H Aug 25 '19 at 16:33
Oh, and I'm thinking EF Core. I forgot the details for EF6. – H H Aug 25 '19 at 16:34
It still insists to get String as a parameter in Include, it keeps saying: "Cannot convert lambda expression to type 'String' because it is not delegate type". I might need to add Room property to ApplicationUser? – Dorki Aug 25 '19 at 16:37
1

Try `Include("User1")` – H H Aug 25 '19 at 16:45
It works! thanks a lot, in order to repeat that for user 2 and 3, how it should look like? – Dorki Aug 25 '19 at 16:46
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/198448/discussion-between-dorki-and-henk-holterman). – Dorki Aug 25 '19 at 16:47
2

You can have multiple `.Include("...")` – H H Aug 25 '19 at 16:51

ASP.NET null reference to a model

2 Answers2