public ActionResult BidOnItem(int id, Bid bid)
        {
            var original = _db.Items.Find(id);
            if (ModelState.IsValid) {
                original.Bids.Add(bid);
                original.NumberOfBids = (from n in _db.Bids where n.Item.Id == id select n).Count()+1;
                _db.SaveChanges();
                return RedirectToAction("Index","Items");
            }
            var vm = new BidOnItemVM
            {
                Item = original
            };

            return View(vm);

        }
        public Bid Create(int value, int currentPrice, string bidderId, string winnerId, int auctionId, IList<string> receiversIds)
        {
            string winnerUsername = string.Empty;

            if (!string.IsNullOrEmpty(winnerId))
            {
                winnerUsername = this.users.GetById(winnerId).UserName.ToString();
            }

            var bid = new Bid
            {
                Value = value,
                CurrentPrice = currentPrice,
                BidderId = bidderId,
                WinnerId = winnerId,
                WinnerUsername = winnerUsername,
                AuctionId = auctionId,
            };

            if (receiversIds[0] == "All")
            {
                bid.Bidders = auctions.GetById(auctionId).Bidders.ToList();
            }
            else
            {
                foreach (var userId in receiversIds)
                {
                    var receiver = this.users.GetById(userId);
                    bid.Bidders.Add(receiver);
                }
            }

            this.bids.Add(bid);
            this.bids.Save();

            return bid;
        }