Dimi Dimi - 1 month ago 25
C# Question

FindAsync and Include LINQ statements

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

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();