SRPTalk.Controllers.PriceDb.GetPriceByIsbn C# (CSharp) Method

        public decimal? GetPriceByIsbn(string isbn)
        {
            var sql = "SELECT Price FROM Prices WHERE Isbn = @isbn";
            using (var conn = new SQLiteConnection(_connectionString))
            {
                conn.Open();
                var sqlCommand = new SQLiteCommand(sql, conn);
                sqlCommand.Parameters.AddWithValue("isbn", isbn);
                var price = (decimal?)sqlCommand.ExecuteScalar();
                conn.Close();
                return price;
            }
        }
    }

        public ViewResult Index(PriceLookup price)
        {
            var connectionString = @"Data Source=" + Server.MapPath("App_Data/prices.s3db");
            var priceDb          = new PriceDb(connectionString);

            if (ModelState.IsValid)
            {
                if (!string.IsNullOrEmpty(price.Upc))
                {
                    priceDb.GetPriceByUpc(price);
                    if (price.Price == null)
                    {
                        ModelState.AddModelError("NotFound", "UPC not found");
                    }
                }
                else if (!string.IsNullOrEmpty(price.Isbn))
                {
                    priceDb.GetPriceByIsbn(price);
                    if (price.Price == null)
                    {
                        ModelState.AddModelError("NotFound", "ISBN not found");
                    }
                }
                else
                {
                    ModelState.AddModelError("Required", "You must enter a UPC or an ISBN");
                }
            }

            return(View(price));
        }