Can you please elaborate on what exactly you're hoping to accomplish and what problem you're having?
Client Certificates allow a client application to authenticate to a server over a HTTPS connection without using a traditional username/password. You can configure Fiddler to use a client certificate to respond to a server's authentication challenges; if you want to use Fiddler when contacting a HTTPS server that requires a client certificate, you MUST configure Fiddler with the client certificate because otherwise the authentication process will fail (mutual authentication breaks MITM attacks).
I suspect you might really be saying: "My .NET code isn't working, but if I use Fiddler to do client certificate authentication it works fine. How can I fix my .NET code?" If that's the case, please share your code.
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