在Web API 2中获取null值而不是数据 [英] Getting null value instead of data in web API 2

问题描述

使用此URI

http：// localhost：2259 / api / ServiceA / 1234



其中isbn = 1234 isbn value在数据库中是1234



我得到Null。虽然我在数据库中有数据应该在这里显示



我尝试过：



我的webapiconfig

with this URI
http://localhost:2259/api/ServiceA/1234"

where isbn=1234 isbn value is 1234 in database

I am getting Null . While i have data in the database which should be shown here

What I have tried:

my webapiconfig

public static class WebApiConfig
   {
       public static void Register(HttpConfiguration config)
       {
           config.MapHttpAttributeRoutes();

           config.Routes.MapHttpRoute(
               name: "DefaultApi",
               routeTemplate: "api/{controller}/{isbn}",
               defaults: new { isbn = RouteParameter.Optional }
           );
       }

和我的服务A控制器

and my service A Controller

public class ServiceAController : ApiController
   {


       [HttpGet]
       public Book GetBook(string isbn)
         {

           using (AppDbContext db = new AppDbContext())

           {

               var query = from b in db.Books

                           where b.ISBN == isbn && b.Source == "Book Store 1"

                           select b;

               return query.SingleOrDefault();

           }

       }
   }

推荐答案

嗯，你得到null因为你的查询WHERE条件与任何记录都不匹配。



使用行在上设置断点并检查 isbn的值。机会很好，它的价值不是你想象的那样。

Well, you're getting null because your query WHERE condition doesn't match any records.

Put a breakpoint on the using line and check the value of isbn. Chances are good its value is not what you think it is.

这篇关于在Web API 2中获取null值而不是数据的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！