How to use Fiddler to debug traffic from Any app (eg. C#/WPF app)

Question

I am tring to debug whats wrong with my HTTP requests from another question here on SO. So i read a bit about Fiddler and wanted to use it to debug my problem. But I can't seem to get traffic from my WPF application to go through Fiddler. I believe I need to configure a proxy. I am using a WebClient for a basic example, but I think i will require a WebRequest later. But for now, with a simple WebClient, how can I get it to go through Fiddler (I believe I have to set proxy to localhost:8888)?

UPDATE:

I don't know if i did the right thing or not but I tried

var wc = new WebClient(); WebProxy proxy = new WebProxy(); proxy.Address = new Uri("http://localhost:8888"); wc.Proxy = proxy; 

but failed - I don't see any traffic in Fiddler

I tried ...

var wc = new WebClient(); WebProxy proxy = new WebProxy("127.0.0.1", 8888); wc.Proxy = proxy; 

still nothing

Answer 1

I found the solution at this fiddler2.com page

Why don't I see traffic sent to http://localhost or http://127.0.0.1?

Internet Explorer and the .NET Framework are hardcoded not to send requests for Localhost through any proxies, and as a proxy, Fiddler will not receive such traffic.

The simplest workaround is to use your machine name as the hostname instead of Localhost or 127.0.0.1. So, for instance, rather than hitting http://localhost:8081/mytestpage.aspx, instead visit http://machinename:8081/mytestpage.aspx.

Answer 2

Maybe a little late, but...

I get around this simply by appending a "dot" to localhost, so instead of accessing localhost, I try to access localhost. (notice the dot at the end of the hostname)

Credit where credit is due: I got this unusual tip from this thread http://www.west-wind.com/weblog/posts/2009/Jan/14/Monitoring-HTTP-Output-with-Fiddler-in-NET-HTTP-Clients-and-WCF-Proxies#596591

Works fine!