The primary problem with your code sample is here:
Fiddler.FiddlerApplication.Startup(0, FiddlerCoreStartupFlags.Default & FiddlerCoreStartupFlags.DecryptSSL);
You're using an & operator when you mean to use an | operator, and since DecryptSSL is already in the Default flags, you can omit the &DecryptSSL
You also don't need this:
oSecureEndpoint = FiddlerApplication.CreateProxyEndpoint(iSecureEndpointPort, true, sSecureEndpointHostname);
... that code is used for creating a proxy endpoint that itself
speaks TLS, an obscure feature of some browsers and not one that you need for your scenario.
When developing any sort of FiddlerCore-based application, you should absolutely attach handlers for OnNotification
as these handlers will often emit useful information when something unexpected occurs.
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