DropDownList problem podczas uruchamiania aplikacji

Witam,

Mam problem z DropDownList, mianowicie podczas uruchamiania lokalnie aplikacji wywala błąd:

Error: There is already an open DataReader associated with this Command which must be closed first.

Wraz z informacją źródła błędu:

Line 51:             @Html.DropDownList("ScreeningId", null, htmlAttributes: new { @class = "form-control" })

Umieszczam dodatkowo pliki View oraz Controller.

public class ReservationsController : Controller
    {
        private AppDbContext db = new AppDbContext();

        // GET: Reservations
        public ActionResult Index()
        {
            return View(db.Reservations.ToList());
        }

        // GET: Reservations/Create
        public ActionResult Create()
        {
            ViewBag.ScreeningId = new SelectList(db.Screenings, "Id", "Description");

            HashSet<int> seats = new HashSet<int>(db.Reservations.Select(x => x.SeatNumber));
            ViewBag.Seats = seats;
            return View();
        }

        
        

        // POST: Reservations/Create
        [HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult Create([Bind(Include = "Id,FirstName,SecondName,Phone,SeatNumber,ScreeningId")] Reservation reservation)
        {
           
            if (ModelState.IsValid)
                {

                // sprawdzamy czy miejsce bylo juz zajete
                if (db.Reservations.Select(x => x.SeatNumber).Contains(reservation.SeatNumber))
                {
                    ViewBag.ScreeningId = new SelectList(db.Screenings, "Id", "Description");
                    return View(reservation);
                }
                else
                {
                    db.Reservations.Add(reservation);
                    db.SaveChanges();
                }
                if (Session["Login"] != null)
                {
                    return RedirectToAction("Index");
                }
                return RedirectToAction("Success");
            }
            

            return View(reservation);
        }

    <div class="form-group">
        @Html.LabelFor(model => model.Screening, "Seans", htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.DropDownList("ScreeningId", null, htmlAttributes: new { @class = "form-control" })
            @Html.ValidationMessageFor(model => model.Screening, "", new { @class = "text-danger" })
        </div>
    </div>

Aplikacja jest umieszczona na hostingu darmowym. Lokalnie gdy uruchamiam, błędu w tym miejscu nie wywala.