Question

我有一个C＃dll来使用Entity Framework查询数据。之后，我使用owin创建一个rest api来引用dll来获取数据。我有两个示例：一个是使用控制台应用程序来访问数据，它没问题。另一个是我将其余的api放在Windows服务中，然后访问它。它返回空。我不知道为什么。

C＃dll：

Answer 1

ef dll：

public class DemoContext:DbContext
{ 
    private static DemoContext _instance;
    public DemoContext() : base("MyDemoConnection")
    {
        Database.SetInitializer(new MigrateDatabaseToLatestVersion<DemoContext, Configuration>());
    }

    public static DemoContext Instance
    {
        get
        {
            if (_instance == null)
            {
                _instance = new DemoContext();
            }
            return _instance;
        }
    }

    public DbSet<Student> Students { get; set; }

    public DbSet<Teacher> Teachers { get; set; }
}

owin api：

public class Startup
{
    public void Configuration(IAppBuilder appBuilder)
    {
        // Configure Web API for self-host. 
        HttpConfiguration config = new HttpConfiguration();
        config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "api/{controller}/{id}",
            defaults: new { id = RouteParameter.Optional }
        );

        appBuilder.UseWebApi(config);
    }
}
public class TeachersController : ApiController
{

    [HttpGet]
    [Route("api/teachers")]
    public HttpResponseMessage Get()
    {
        try
        {
            var _context = DemoContext.Instance;
            var teachers = _context.Teachers.ToList();
            var response = Request.CreateResponse(HttpStatusCode.OK, teachers);
            return response;
        }
        catch (Exception ex)
        {
            return Request.CreateResponse(HttpStatusCode.OK, ex.Message);
        }

    }
}

控制台应用：

class Program
{
    static void Main(string[] args)
    {
        string baseAddress = "http://localhost:9000/";

        // Start OWIN host 
        using (WebApp.Start<Startup>(url: baseAddress))
        {
            // Create HttpCient and make a request to api/values 
/*                HttpClient client = new HttpClient();
            client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
             var response = client.GetAsync(baseAddress + "api/values").Result;
            var result = response.Content.ReadAsStringAsync().Result;
            Console.WriteLine(result);*/
            Console.ReadLine();
        }
    }
}

windowservice：

public partial class HostOwin : ServiceBase
{
    private IDisposable owin;
    public HostOwin()
    {
        InitializeComponent();
    }

    protected override void OnStart(string[] args)
    {
        string baseAddress = "http://localhost:9000/";
        owin = WebApp.Start<Startup>(url: baseAddress);

    }

    protected override void OnStop()
    {
        owin.Dispose();
    }
}

访问LocalDb的Windows服务返回空

1 个答案: