Configure .NET Applications

To allow the .NET Framework to automatically connect to Fiddler, start Fiddler Classic before starting the .NET application.

To temporarily connect a .NET application to Fiddler Classic, use the GlobalProxySelection class to set a proxy:

System.Net.WebRequest.DefaultWebProxy = new System.Net.WebProxy("127.0.0.1", 8888);

Or, specify a proxy inside the yourappname.exe.config file.

• If the .NET application is running in your current user account, add the following content inside the configuration section:

  <configuration>
   <system.net>
    <defaultProxy>
     <proxy bypassonlocal="false" usesystemdefault="true" />
    </defaultProxy>
   </system.net>
  </configuration>
  

See MSDN for more on this topic.

• If the .NET application is running in a different user account (for example, a Windows service), edit the machine.config file:

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

Or, manually specify the proxy on an individual WebRequest object:

    objRequest = (HttpWebRequest)WebRequest.Create(url);
    objRequest.Proxy= new WebProxy("127.0.0.1", 8888);

Note: Important: Regardless of other settings, .NET will always bypass the Fiddler Classic proxy for URLs containing localhost. So, rather than using localhost, change your code to refer to the machine name. For instance:

• This URL will not appear in Fiddler:

  http://localhost/X509SignCodeService/X509SigningService.asmx

• This URL will appear in Fiddler:

  http://mymachine/X509SignCodeService/X509SigningService.asmx

Configure .NET Core Applications

Setup the proxy via netsh tool in commmand line the following way

see Netsh Docs for more info on this topic

    netsh winhttp set proxy 127.0.0.1:8888

To remove the proxy use the following

    netsh winhttp reset proxy