public ActionResult Add(MonitorViewModel viewmodel)
        {
            ViewBag.LM = context.Stocks.ToList().Where(x => x.category == "Monitor");
            List <Stock>          slist = new List <Stock>(context.Stocks.ToList().Where(x => x.category == "Monitor"));
            List <SelectListItem> li    = new List <SelectListItem>();

            foreach (var item in slist)
            {
                var man = li.Find(x => x.Value == item.manufacturer);
                if (man == null)
                {
                    li.Add(new SelectListItem {
                        Text = item.manufacturer, Value = item.manufacturer
                    });
                }
            }
            ViewBag.MM = li;
            if (ModelState.IsValid)
            {
                try
                {
                    Stock stock = context.Stocks.FirstOrDefault(m => m.model.Equals(viewmodel.modelName) &&
                                                                m.manufacturer.Equals(viewmodel.manufacturer) &&
                                                                m.category.Equals("Monitor"));

                    if (stock != null && stock.quantity != 0)
                    {
                        AssetLogic al    = new AssetLogic();
                        var        asset = new Asset
                        {
                            manufacturer     = viewmodel.manufacturer,
                            serialNumber     = viewmodel.serialNumber,
                            dateadded        = viewmodel.dateAdded,
                            warranty         = viewmodel.warranty + " Months",
                            costprice        = viewmodel.costprice,
                            InvoiceNumber    = viewmodel.InvoiceNumber,
                            depreciationcost = al.depreciationCost(viewmodel.dateAdded, viewmodel.costprice)
                        };
                        var monitor = new Monitor
                        {
                            serialNumber  = viewmodel.serialNumber,
                            manufacturer  = viewmodel.manufacturer,
                            modelName     = viewmodel.modelName,
                            warranty      = viewmodel.warranty + " Months",
                            dateAdded     = viewmodel.dateAdded,
                            displaySize   = viewmodel.displaySize,
                            InvoiceNumber = viewmodel.InvoiceNumber
                        };
                        stock.quantity = stock.quantity - 1;
                        _repo.Insert(asset, monitor);
                        _repo.Save();
                        context.SaveChanges();
                        TempData["Success"] = "Asset has been added!";
                    }
                    else
                    {
                        ViewBag.Message = "Asset model not available in stock. Update your stock.";
                    }
                }
                catch (Exception e)
                {
                    ViewBag.Message = "Asset not added. Error: " + e.Message;
                }
            }
            ModelState.Clear();
            return(View(viewmodel));
        }