前台：ShowDetail("英伦学院派马夹");

function ShowDetail(productId) {
            // make an ajax call to the web service to get Car detail
         
           
            $.ajax({
                type: "GET",
                contentType: "application/json; charset=utf-8",
                url: "ProductService.asmx/GetProductByIds",
                data: "{Productname:" + productId + "}",
                dataType: "json",
             
                success: SelectProductByIdSuccess,
                error: function (XMLHttpRequest, textStatus, errorThrown) {
                    alert(errorThrown + ':' + textStatus);
                }
            });

后台：  /// <summary>
        /// 根据商品名称查询商品
        /// </summary>
        /// <param name="id">商品名称</param>
        /// <returns>商品</returns>
        [WebMethod]
        [ScriptMethod(ResponseFormat = ResponseFormat.Json, UseHttpGet = true)]
        public List<Product> GetProductByIds(string Productname)
        {
            return dataSource.GetProductByName(Productname);
        }
    }

  public List<Product> GetProductByName(string name)
        {
            return productList.Where(p => p.ProductName == name).ToList();
        }

 private List<Product> productList = new List<Product>()
        {
            new Product(){ProductId=1,ProductName="笔记本", Price=10000M, Stock=10},
            new Product(){ProductId=2,ProductName="格子绒长袖衬衫", Price=90M, Stock=20},
            new Product(){ProductId=3,ProductName="纯棉长袖T恤", Price=99M, Stock=40},
            new Product(){ProductId=4,ProductName="炫彩T恤", Price=67M, Stock=30},
            new Product(){ProductId=5,ProductName="直筒裤男牛仔裤", Price=100M, Stock=20},
             new Product(){ProductId=6,ProductName="[无印严选]纯色V领长袖T恤", Price=67M, Stock=50},
            new Product(){ProductId=7,ProductName="英伦学院派马夹", Price=44M, Stock=40},
            new Product(){ProductId=8,ProductName="纯棉连帽宽松卫衣", Price=66M, Stock=30},
            new Product(){ProductId=9,ProductName="纯棉多口袋工装裤", Price=80M, Stock=990},
            new Product(){ProductId=10,ProductName="假两件长袖T恤", Price=89M, Stock=30},
        };

调试错误：{"Message":"Web 服务调用无效，参数“Productname”缺少值。","StackTrace":"   在 System.Web.Script.Services.WebServiceMethodData.CallMethod(Object target, IDictionary`2 parameters)\r\n   在 System.Web.Script.Services.WebServiceMethodData.CallMethodFromRawParams(Object target, IDictionary`2 parameters)\r\n   在 System.Web.Script.Services.RestHandler.InvokeMethod(HttpContext context, WebServiceMethodData methodData, IDictionary`2 rawParams)\r\n   在 System.Web.Script.Services.RestHandler.ExecuteWebServiceCall(HttpContext context, WebServiceMethodData methodData)","ExceptionType":"System.InvalidOperationException"}