Fiddler Not Capturing Traffic from my C# Application in Windows 8

18
votes

I have recently upgraded to a new computer with Windows 8. I have installed Fiddler, yet I am having problems capturing traffic sent and received from my C# application. I never had this issue on Windows 7, so I assume its a Windows 8 issue.

The application is an ordinary WinForms application using C# 5.0 and .NET 4.5. I am using Visual Studio 2012.

Any ideas how to get around this as I'm having a hard time debugging my application without it.

Fiddler captures traffic from Chrome and Firefox with no issues, just not my application. I have also loaded another application that I developed, and that works fine.

It may be worth noting that this is the first application I've developed that uses HttpClient to make Http requests. Could that be causing any issues?

Edit: I am using the Fiddler Application to monitor traffic. I am not connecting to localhost. I am connect to web API's.

1
c#fiddler
Are you connecting to localhost? – Rik
Have you checked that help page: fiddler2.com/documentation/Configure-Fiddler/Tasks/… – Simon Mourier
Do you use the Fiddler application to capture the traffic of your app, or do you use the Fiddler C# lib from your app? – kol
I am not connecting to local host. I use the Fiddler application to capture traffic. – James Jeffery
@kol I am using a WinForms app, not a metro style app. – James Jeffery

1 Answers

20
votes

Step #1 is to try starting Fiddler before starting your application. This helps the default configuration, whereby .NET applications pick up the system proxy when they start and are oblivious to proxy changes after they start.

Step #2, if the first step doesn't work, is to explicitly configure your process to use the proxy by editing the app.exe.config file or the machine.config file, or by setting the Proxy property on the request object.