问找不到WebApi控制器

EN

public class MilestonesController : ApiController
{
    // GET api/milestones
    public IEnumerable<string> Get()
    {
        return new string[] { "M#1", "M#2" };
    }

    // GET api/milestones/5
    public string Get(int id)
    {
        return "M with {id}";
    }

    // POST api/milestones
    public void Post([FromBody]string value)
    {
    }

    // PUT api/milestones/5
    public void Put(int id, [FromBody]string value)
    {
    }

    // DELETE api/milestones/5
    public void Delete(int id)
    {
    }
}

No HTTP resource was found that matches the request URI 'http://localhost:59493/api/milestones'.

No type was found that matches the controller named 'milestones'.

public static class WebApiConfig
{
    public static void Register(HttpConfiguration config)
    {
        // Web API configuration and services

        // Web API routes
        config.MapHttpAttributeRoutes();

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

public class WebApiApplication : System.Web.HttpApplication
{
    protected void Application_Start()
    {
        AreaRegistration.RegisterAllAreas();
        GlobalConfiguration.Configure(WebApiConfig.Register);
        FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
        WebApiConfig.Register(GlobalConfiguration.Configuration);
        RouteConfig.RegisterRoutes(RouteTable.Routes);
        BundleConfig.RegisterBundles(BundleTable.Bundles);
    }
}