Using Fiddler with .NET Framework Winforms Apps

Open exe config file for the environment in a text editor.

Under <configuration> element place

 <!-- The following section is to force use of Fiddler for all applications, including those running in service accounts -->
    <system.net>
        <defaultProxy enabled = "true"
                      useDefaultCredentials = "true">
            <proxy autoDetect="false"
                   bypassonlocal="false"
                   proxyaddress="http://127.0.0.1:8888"
                   usesystemdefault="false" />
        </defaultProxy>
    </system.net>