Enabling Cross-Origin Requests in ASP.NET Web API 2


Enable CORS

Now let’s enable CORS in the WebService app. First, add the CORS NuGet package. In Visual Studio, from the Toolsmenu, select Library Package Manager, then select Package Manager Console. In the Package Manager Console window, type the following command:

Install-Package Microsoft.AspNet.WebApi.Cors

This command installs the latest package and updates all dependencies, including the core Web API libraries. User the -Version flag to target a specific version. The CORS package requires Web API 2.0 or later.

Open the file App_Start/WebApiConfig.cs. Add the following code to the WebApiConfig.Register method.

using System.Web.Http;
namespace WebService
    public static class WebApiConfig
        public static void Register(HttpConfiguration config)
            // New code

                name: "DefaultApi",
                routeTemplate: "api/{controller}/{id}",
                defaults: new { id = RouteParameter.Optional }

Next, add the [EnableCors] attribute to the TestController class:

using System.Net.Http;
using System.Web.Http;
using System.Web.Http.Cors;

namespace WebService.Controllers
    [EnableCors(origins: "http://mywebclient.azurewebsites.net", headers: "*", methods: "*")]
    public class TestController : ApiController
        // Controller methods not shown...

For the origins parameter, use the URI where you deployed the WebClient application. This allows cross-origin requests from WebClient, while still disallowing all other cross-domain requests. Later, I’ll describe the parameters for[EnableCors] in more detail.

Do not include a forward slash at the end of the origins URL.

Redeploy the updated WebService application. You don’t need to update WebClient. Now the AJAX request from WebClient should succeed. The GET, PUT, and POST methods are all allowed.

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