How do I log unhandled exceptions in ASP.NET MVC?

Question

Here's what I'm trying to do in my Global.asax.vb:

Public Class MvcApplication
    Inherits System.Web.HttpApplication

    Shared Sub RegisterRoutes(ByVal routes As RouteCollection)
        routes.IgnoreRoute("{resource}.axd/{*pathInfo}")
        routes.MapRoute( _
            "Error", _
            "error.html", _
            New With {.controller = "Error", _
                      .action = "FriendlyError"} _
        )
        ...
        'other routes go here'
        ...
    End Sub

    Sub Application_Start()
        RegisterRoutes(RouteTable.Routes)
    End Sub

    Sub Application_Error(ByVal sender As Object, ByVal e As EventArgs)
        ...
        'code here logs the unhandled exception and sends an email alert'
        ...
        Server.Transfer("http://www.example.com/error.html")
    End Sub

End Class

But that Server.Transfer fails:

Invalid path for child request 'http://www.example.com/error.html'. A virtual path is expected.

How do I fix this? Or, what's a better way for me to do this?

Joseph · Accepted Answer · 2009-05-01 15:57:11Z

9

I just found this on Scott Hanselman's blog here called ELMAH which is an Error Logger/Handler that you can use without having to change your code. You might want to look into it, since it seems to work nicely with MVC.

answered May 1, 2009 at 15:57

Joseph

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3 Comments

Jarrod Dixon Over a year ago

We use a modified version of ELMAH here on Stack Overflow - it's very good.

Gavin Miller Over a year ago

@Jarrod - What types of things have you guys included in your fork?

MikeJ Over a year ago

ELMAH rules - its more helpful than log4net was. IMHO.

Gavin Miller · Accepted Answer · 2009-05-01 16:12:20Z

3

ELMAH is an excellent error handler for catching unhandled exceptions. It plugs seamlessly into your web application via HttpModules and has various options for notification and logging.

Features:

SQL, XML, SQLite, InMemory Logging
Email notification
RSS feed
Detailed! logging of exceptions
Easy integration
Error Signalling - signal the error handler of an error while "dieing nicely" for the user

And FYI, SO uses ELMAH, albeit a forked version. This is the best architectural explanation and setup tutorial

edited May 1, 2009 at 16:12

answered May 1, 2009 at 16:04

Gavin Miller

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Comments

JonoW · Accepted Answer · 2009-05-01 15:54:59Z

2

You have to specifiy a virtual path, i.e. a path relative to the application base (i.e. no paths external to the app), so something like: Server.Transfer("error.html") or Server.Transfer("/error.html") or Server.Transfer("~/error.html")

answered May 1, 2009 at 15:54

JonoW

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4 Comments

Zack Peterson Over a year ago

"~/error.html": Error executing child request for /error.html.

Zack Peterson Over a year ago

"/error.html": Error executing child request for /error.html.

JonoW Over a year ago

I just did the same tests, they all worked, except if I put in an incorrect filename, then I get "Error executing child request for /test_WRONG.html.". Are you sure that error.html exists in the root?

Zack Peterson Over a year ago

It does not exist. It should route to the FriendlyError view of the Error controller.

Peter J · Accepted Answer · 2009-05-01 17:03:43Z

2

By default, ASP.NET MVC applications have a view Shared/Error.aspx, inheriting from

System.Web.Mvc.ViewPage<System.Web.Mvc.HandleErrorInfo>

If your controller uses the attribute [HandleError], all exceptions will continue to bubble until caught, and they will end up on that page.

I simply added an inline Page_Load (valid in this case since it's the end of the line):

<script runat="server">
  Sub Page_Load(ByVal Sender As System.Object, ByVal e As System.EventArgs)
    MyExceptionHandlerService.LogException("exceptionsource", this.Model.Exception)
  End Sub
</script>

After it, the friendly "Sorry..." message. It definitely looks like ELMAH is more robust, but for my needs, this was sufficient.

edited May 1, 2009 at 17:03

answered May 1, 2009 at 16:20

Peter J

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