Question

I’ve been scanning forums for an implementation of the Exception Management Application Block (EMAB) in an ASP.NET MVC (MVC3) application.

There’s a lot of talk about ELMAH and NLog as well as handling via the global.asax (http://s151.codeinspot.com/q/694875) Vs an ErrorController (http://www.davidjuth.com/asp-net-mvc-error-handler.aspx) approach as well as leveraging the [HandleError] decoration

We are looking at standardising our Exception Management of our MVC apps with EMAB but I can’t seem to find any specific examples that provide an all round solution.

Does anyone have any links or can explain exactly how you might utilise EMAB within the MVC framework

Answer 1

I decided on the approach below…

//**In Global.asax

    protected void Application_Error(object sender, EventArgs e)
    {
        Exception originalError = Server.GetLastError();
        Exception replacedError;

        if (ExceptionPolicy.HandleException(originalError, "Global Policy", out replacedError))
        {
            Exception ex = replacedError ?? originalError;
            if (ex.InnerException != null)
            {
                ex = ex.InnerException;
            }
            var httpException = ex as HttpException;
            HttpApplication httpApplication = this.Context.ApplicationInstance;

            string message = Utility.GetFullMessage(httpApplication, ex, "::");
            string messageHtml = Utility.GetFullMessage(httpApplication, ex, "<br/>");

            LogEntry logEntry = new LogEntry();
            logEntry.EventId = 100;
            logEntry.Priority = 2;
            logEntry.Message = ex.Message + "::" + message;
            Logger.Write(logEntry);

            Response.Clear();
            Server.ClearError();

            var routeData = new RouteData();
            routeData.Values["controller"] = "Error";
            routeData.Values["action"] = Constants.ErrorGeneralKey; //"General"
            routeData.Values["message"] = ex.Message;
            routeData.Values["fullMessage"] = messageHtml;
            Response.StatusCode = 500;

            if (httpException != null)
            {
                Response.StatusCode = httpException.GetHttpCode();

                switch (Response.StatusCode)
                {
                    case 403:
                        routeData.Values["action"] = "Http403";
                        break;

                    case 404:
                        routeData.Values["action"] = "Http404";
                        break;

                    default:
                        routeData.Values["httpStatusCode"] = Response.StatusCode;
                        break;
                }
            }
            IController errorController = new ErrorController();
            var rc = new RequestContext(new HttpContextWrapper(Context), routeData);
            errorController.Execute(rc);
        }
    }

//**In helper class

    public static string GetFullMessage(HttpApplication httpApplication, Exception ex, string delimiter)
    {
        return "StackTrace: " + ex.StackTrace
                    + delimiter + "User: " + ((httpApplication.User == null) ? "<null>" : httpApplication.User.Identity.Name)
                    + delimiter + "Data: " + GetExceptionData(ex.Data)
                    + delimiter + "Version: " + httpApplication.Request.Browser.Version
                    + delimiter + "Browser: " + httpApplication.Request.Browser.Browser
                    + delimiter + "Major Version: " + httpApplication.Request.Browser.MajorVersion.ToString()
                    + delimiter + "Minor Version: " + httpApplication.Request.Browser.MinorVersion.ToString()
                    + delimiter + "Javascript Version: " + httpApplication.Request.Browser.JScriptVersion.ToString()
                    + delimiter + "Ecma Script Version: " + httpApplication.Request.Browser.EcmaScriptVersion.ToString()
                    + delimiter + "Platform: " + httpApplication.Request.Browser.Platform
                    + delimiter + "Source: " + ex.Source
                    + delimiter + "Form: " + httpApplication.Request.Form.ToString()
                    + delimiter + "QueryString: " + httpApplication.Request.QueryString.ToString()
                    + delimiter + "TargetSite: " + ex.TargetSite;
    }

//**In Error controller

    public ActionResult General(string httpStatusCode, string message, string fullMessage)
    {
        errorViewModel.RootCause = Enums.RootCause.General;
        errorViewModel.HttpStatusCode = httpStatusCode;
        errorViewModel.Message = message;
        errorViewModel.FullMessage = fullMessage;
        return View("Error", errorViewModel);
    }

    public ActionResult Http404()
    {
        errorViewModel.RootCause = Enums.RootCause.NotFound;
        return View("Error", errorViewModel);
    }

    public ActionResult Http403()
    {
        errorViewModel.RootCause = Enums.RootCause.Forbidden;
        return View("Error", errorViewModel);
    }