Lazy loading not working when trying to access related entity

Question

This is microsoft's scaffolding code for the action Details of the entity MyEntity:

public async Task<ActionResult> Details(Guid? id)
{
    if (id == null)
    {
        return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
    }
    MyEntity myEntity = await db.MyEntities.FindAsync(id);
    if (myEntity == null)
    {
        return HttpNotFound();
    }
    return View(myEntity);
}

Now let's say I want to display the name of the owner of this entity in details.cshtml, if I write the following code:

<dt>
    Owner
</dt>
<dd>
    @Html.DisplayFor(m => m.User.FullName)
</dd>

User shows up as null, even after trying to access Model.User to trigger the lazy loading.

Edit: Adding the model as requested

public class MyEntity
{
    public Guid? Id { get; set; }
    public string Name { get; set; }
    public ApplicationUser User { get; set; }
}

Can you post your model? Assuming you have related entities, you can use .Include() to load related entities (Eager Loading). Or if you just access a navigation property, it will use lazy loading. — lopezbertoni
– lopezbertoni, Commented Feb 19, 2014 at 12:24
Isn't that what I'm already doing in my DisplayFor line? (accessing the navigation property) — Luis Ferrao
– Luis Ferrao, Commented Feb 19, 2014 at 12:31
I've testing "just accessing" the navigation property, it simply does not work — Luis Ferrao
– Luis Ferrao, Commented Feb 19, 2014 at 13:43
Put a stop before rendering the View and see if your model if being loaded correctly. — lopezbertoni
– lopezbertoni, Commented Feb 19, 2014 at 14:21

Matt Tabor · Accepted Answer · 2014-02-19 12:28:19Z

1

Add .Include("User") to your linq query.

answered Feb 19, 2014 at 12:28

Matt Tabor

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7 Comments

Luis Ferrao Over a year ago

This is my linq query: db.MyEntities.FindAsync(id). If I add Include(User) then I can't FindAsync() anymore, I guess I could always resort to Single() but is this really the right way of doing this? It's strange that I have to change the FindAsync() pattern just to include related entities.

Matt Tabor Over a year ago

try using SingleOrDefaultAsync()

Luis Ferrao Over a year ago

Also, will it load the users for every MyEntity or just for the found entity?

Matt Tabor Over a year ago

it will load the single "User" entity that is attached to the MyEntity model

Matt Tabor Over a year ago

and make sure you use Include("User") with quotes

|

brandera33 · Accepted Answer · 2014-04-30 15:37:07Z

0

I was running into the same issue, and Matt's answer led me down a similar road. I thought I'd share what I found.

This article indicates that Lazy Loading doesn't fit well with the Async pattern. Good to know.

With that, I looked into eager loading. I found my answer there.

MyEntity myEntity = await db.MyEntities.Where(m => m.Id == id)
                                       .Include(m => m.User)
                                       .FirstOrDefaultAsync();

Hope that helps someone else!

answered Apr 30, 2014 at 15:37

brandera33

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