c# - FindAsync and Include LINQ statements

Question

The code I have got so far works fine

public async Task<ActionResult> Details(Guid? id)
{
    if (id == null)
    {
        return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
    }

    ItemDetailModel model = new ItemDetailModel();
    model.Item = await db.Items.FindAsync(id);
    if (model.Item == null)
    {
        return HttpNotFound();
    }

    return View(model);
}

But I want to include 1 table more and cannot use FindAsync

public async Task<ActionResult> Details(Guid? id)
{
    if (id == null)
    {
        return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
    }

    ItemDetailModel model = new ItemDetailModel();
    model.Item = await db.Items.Include(i=>i.ItemVerifications).FindAsync(id);

    if (model.Item == null)
    {
        return HttpNotFound();
    }           

    return View(model);
}

So I am facing this error

Severity Code Description Project File Line Suppression State Error CS1061 'IQueryable' does not contain a definition for 'FindAsync' and no extension method 'FindAsync' accepting a first argument of type 'IQueryable' could be found (are you missing a using directive or an assembly reference?)

Any clue how to fix it?

Answer 1

The simplest is to use FirstOrDefaultAsync or SingleOrDefaultAsync instead:

model.Item = await db.Items.Include(i => i.ItemVerifications)
    .FirstOrDefaultAsync(i => i.Id == id.Value);

The reason you are getting the error is because Find / FindAsync methods are defined for DbSet<T>, but the result of Include is IQueryable<T>.

Another way is to combine FindAsync with explicit loading:

model.Item = await db.Items.FindAsync(id);
if (model.Item == null)
{
    return HttpNotFound();
}
await db.Entry(model.Item).Collection(i => i.ItemVerifications).LoadAsync();