public ActionResult Index()
        {
            ProductSearchModel _ProductViewModel = new ProductSearchModel
            {
               Sizes = processManager.GetSizes().Select(x => new SelectListItem
                    {
                        Value = x.SizeId.ToString(),
                        Text = x.SizeName
                    }),
               Brands = processManager.GetBrands().Select(x => new SelectListItem
               {
                   Value = x.BrandId.ToString(),
                   Text = x.BrandName
               }),
               Colours = processManager.GetColours().Select(x => new SelectListItem
               {
                   Value = x.ColourId.ToString(),
                   Text = x.ColourName
               }),
               Customers = processManager.GetCustomers().Select(x => new SelectListItem
               {
                   Value = x.CustomerId.ToString(),
                   Text = x.CustomerName
               }),
               Products = processManager.GetProducts()
            };

            return View(_ProductViewModel);
        }
        public ActionResult Index(string searchString , int SizeID = -1, int BrandID = -1, int ColourID = -1, int CustomerID = -1)
        {
            ProductSearchParameters _Params = new ProductSearchParameters();

            if (SizeID != -1)
            {
                _Params.SizeIds.Add(SizeID);
            }

            if (BrandID != -1)
            {
                _Params.BrandIds.Add(BrandID);
            }

            if (ColourID != -1)
            {
                _Params.ColourIds.Add(ColourID);
            }

            if (searchString.Length > 0)
            {
                _Params.SearchString = searchString;
            }

            ProductSearchModel _ProductViewModel = new ProductSearchModel
            {
                Sizes = processManager.GetSizes().Select(x => new SelectListItem
                {
                    Value = x.SizeId.ToString(),
                    Text = x.SizeName
                }),
                Brands = processManager.GetBrands().Select(x => new SelectListItem
                {
                    Value = x.BrandId.ToString(),
                    Text = x.BrandName
                }),
                Colours = processManager.GetColours().Select(x => new SelectListItem
                {
                    Value = x.ColourId.ToString(),
                    Text = x.ColourName
                }),
                Customers = processManager.GetCustomers().Select(x => new SelectListItem
               {
                   Value = x.CustomerId.ToString(),
                   Text = x.CustomerName
               })
            };

            if (CustomerID != -1)
            {
                _ProductViewModel.Products = processManager.CustomerProductSearch(CustomerID, _Params);
            }
            else
            {
                _ProductViewModel.Products = processManager.ProductSearch(_Params);
            }
            return View(_ProductViewModel);
        }