public static IQueryable<PetShop.Core.Data.Inventory> ByItemId(this IQueryable<PetShop.Core.Data.Inventory> queryable, string itemId, params string[] additionalValues)
        {
            var itemIdList = new List<string> { itemId };

            if (additionalValues != null)
                itemIdList.AddRange(additionalValues);

            if (itemIdList.Count == 1)
                return queryable.ByItemId(itemIdList[0]);

            return queryable.ByItemId(itemIdList);
        }
        public static IQueryable<Petshop.Data.Entities.Cart> ByItemId(this IQueryable<Petshop.Data.Entities.Cart> queryable, System.String itemId, params System.String[] additionalValues)
        {
            var itemIdList = new List<System.String> { itemId };

            if (additionalValues != null)
                itemIdList.AddRange(additionalValues);

            if (itemIdList.Count == 1)
                return queryable.ByItemId(itemIdList[0]);

            return queryable.ByItemId(itemIdList);
        }