webApi裡設定全域性異常返回格式

今天為了設定api返回格式統一，在網上找了一推資料，各種資料參差不齊的，最後自己搗鼓，終於弄出來了，直接上程式碼

    /// <summary>
    /// 訊息代理處理，用來捕獲這些特殊的異常資訊
    /// </summary>
    public class CustomErrorMessageDelegatingHandler : DelegatingHandler
    {
        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
        {
            return base.SendAsync(request, cancellationToken).ContinueWith<HttpResponseMessage>((responseToCompleteTask) =>
            {
                HttpResponseMessage response = responseToCompleteTask.Result;
                HttpError error = null;
                if (response.TryGetContentValue<HttpError>(out error))
                {
                    //自定義錯誤處理
                    //error.Message = "這個介面調用出錯了";
                }
                if (error != null)
                {   //這是本人建立的一個返回類                 
                    var resultMsg = new ResultMsg { StatusCode = (int)StatusCodeEnum.HttpUrlEror, Info =error.MessageDetail  };
 

                    return new HttpResponseMessage { Content = new StringContent(resultMsg.ToJson(), 
                        System.Text.Encoding.GetEncoding("UTF-8"), "application/json"), StatusCode = HttpStatusCode.OK };
                }
                else
                {
                    return response;
                }
            });
        }
    }
 

 protected void Application_Start()
        {
            AreaRegistration.RegisterAllAreas();
            //FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
            //RouteConfig.RegisterRoutes(RouteTable.Routes);
            //BundleConfig.RegisterBundles(BundleTable.Bundles);
            GlobalConfiguration.Configure(WebApiConfig.Register);
            GlobalConfiguration.Configuration.Filters.Add(new ErrorHandler());
 

        }

{
  "StatusCode": 404,
  "Info": "在控制器“StudyTask”上找不到與該請求匹配的操作。",
  "Data": null
}