Filter in WebApi

//Creamos el filtro
    public class EnteroFilter : System.Web.Http.Filters.ActionFilterAttribute
    {
        public override void OnActionExecuting(HttpActionContext filterContext)
        {
            if (!filterContext.ModelState.IsValid)
            {
                if (filterContext.ActionArguments.TryGetValue("id", out object value))
                {
                    if (null == value)
                    {
                        filterContext.Response =
                            filterContext.Request
                            .CreateResponse(
                                HttpStatusCode.BadRequest,
                            new { Code = HttpStatusCode.BadRequest, reason = "data invalida para param Id" });
                    }
                }
                //o bien para obtener todos los errores
                var errores = filterContext
                    .ModelState
                    .Values
                    .Select((x, index) =>
                    new
                    {
                        key = filterContext.ModelState.Keys.ElementAt(index),
                        error = x.Errors[index].Exception.InnerException.Message //validar que tenga innerException
                    });
            }
        }
    }



//Registrar el filtro
//en WebApiConfig.cs
  public static class WebApiConfig
    {
        public static void Register(HttpConfiguration config)
        {
            // Web API configuration and services
            //...
        }

        internal static void RegisterGlobalFilters(HttpFilterCollection filters)
        {
               filters.Add(new EnteroFilter());
        }
    }
//en global.asax
public class WebApiApplication : System.Web.HttpApplication
    {
        protected void Application_Start()
        {
        //...
            WebApiConfig.RegisterGlobalFilters(GlobalConfiguration.Configuration.Filters);
        //...


        }
    }

//Usar el filtro
 public class ValuesController : ApiController
    {
        // GET api/values/5
        [EnteroFilter]
        public string Get(int id)
        {
            return "value";
        }
    }