Web Api -异常不记录日志

我有以下类

    public class WebApiExceptionLoggingFilter : ExceptionFilterAttribute
{
    private readonly ILog _logger;
    public WebApiExceptionLoggingFilter(ILog logger)
    {
        this._logger = logger;
    }
    public override void OnException(HttpActionExecutedContext filterContext)
    {
        //Logging Exception
        _logger.Error("An unhandled exception was thrown", filterContext.Exception);
        //Changing exception message to something generic.
        var exceptionMessage = "An error occurred and logged during processing of this application.";
        //Throwing a proper message for the client side
        var message = new HttpResponseMessage(HttpStatusCode.InternalServerError)
        {
            Content = new StringContent(exceptionMessage),
            ReasonPhrase = exceptionMessage
        };
        throw new HttpResponseException(message);
    }
}

我将它注册为:

        public static void Register(HttpConfiguration config)
    {
        // Web API configuration and services
        // Web API routes
        config.MapHttpAttributeRoutes();
        config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "api/{controller}/{action}/{id}",
            defaults: new { id = RouteParameter.Optional }
        );
        config.Filters.Add(new WebApiExceptionLoggingFilter(LogManager.GetLogger("Web Api Unhandled Exception Logger")));
    }

我有另一个过滤器属性注册为我的mvc控制器，它是注册在FilterConfig.cs文件。当控制器动作中发生异常时，将通过log4net记录到windows事件查看器。当在调用web api控制器动作时发生异常时，上面处理程序中的OnException方法被击中并调用_logger.log，但没有任何内容被记录到事件查看器中。我错过什么了吗?