Enable CORS on my Web API not working

Question

I have the following Web API, self hoseted:

public class ApiShell : IApiShell { private IActorSystemSettings _settings; public ApiShell(IActorSystemSettings settings) { _settings = settings; } IDisposable _webApp; public void Start() { _webApp = WebApp.Start<Startup>(_settings.SystemUrl); Console.WriteLine($"Web server running at '{_settings.SystemUrl}'"); } public void Stop() { _webApp.Dispose(); } internal class Startup { //Configure Web API for Self-Host public void Configuration(IAppBuilder app) { var config = new HttpConfiguration(); config.EnableCors(); config.MapHttpAttributeRoutes(); //default route config.Routes.MapHttpRoute( name: "DefaultApi", routeTemplate: "api/{controller}/{id}", defaults: new { id = RouteParameter.Optional }); config .EnableSwagger(c => c.SingleApiVersion("v1", "Web API")) .EnableSwaggerUi(); app.UseWebApi(config); config.DependencyResolver = new AutofacWebApiDependencyResolver(IoC.Container); } } }

As soon as I would like to Enable Cors, by adding the following line, config.EnableCors(); my Web API is not reachable through Swagger anymore and I get the following reponse:

<Error> <Message>An error has occurred.</Message> <ExceptionMessage> The object has not yet been initialized. Ensure that HttpConfiguration.EnsureInitialized() is called in the application's startup code after all other initialization code. </ExceptionMessage> <ExceptionType>System.InvalidOperationException</ExceptionType> <StackTrace> at System.Web.Http.Routing.RouteCollectionRoute.get_SubRoutes() at System.Web.Http.Routing.RouteCollectionRoute.GetRouteData(String virtualPathRoot, HttpRequestMessage request) at System.Web.Http.HttpRouteCollection.GetRouteData(HttpRequestMessage request) at System.Web.Http.Dispatcher.HttpRoutingDispatcher.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) at System.Net.Http.DelegatingHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) at System.Web.Http.HttpServer.<SendAsync>d__24.MoveNext() </StackTrace> </Error>

I have tried setting the HttpConfiguration.EnsureInitialized(), but this results in the following error:

Could not load file or assembly 'System.Web.Cors, Version=5.2.3.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.'

I have installed the following version of Microsoft.AspNet.WebApi.Cors

Install-Package Microsoft.AspNet.WebApi.Cors.cs -Version 5.2.3

How can I enable CORS in my web api?

Marcus Höglund · Accepted Answer · 2018-05-20 10:42:10Z

1

You forgot to tell the AppBuilder to use cors.

Try and add the following line in the Startup Configuration method

app.UseCors(CorsOptions.AllowAll);

answered May 20, 2018 at 10:42

Marcus Höglund

16.9k11 gold badges53 silver badges72 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

monstertjie_za Over a year ago

In what namespace does this sit?

Marcus Höglund Over a year ago

@monstertjie_za just realized this options is from the Microsoft.Owin.Cors. If you don't use Owin, just forget it

hosam hemaily · Accepted Answer · 2018-05-20 11:23:43Z

you can enable corse by the following sample

using System.Web.Http; using System.Web.Http.Cors; [EnableCors(origins: "*", headers: "*", methods: "*")] public class EvalSamplesController : ApiController { [HttpGet] public List<EvalSamplesViewModel> GetHeaderList() { List<EvalSamplesViewModel> simpleModel = obj.ReadAllList(); return simpleModel; } }

and in the app_start in WebApiConfig put the following line in the method Register

public static void Register(HttpConfiguration config) { config.EnableCors(); ///////// }

Collectives™ on Stack Overflow

Enable CORS on my Web API not working

2 Answers 2

2 Comments

Comments

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Related