Forcing a .NET application proxy via web.config or app.config
This lets you force a proxy for a .NET application including web sites, running under any user or service account. Very useful for proxying via Fiddler.
<system.net>
<defaultProxy>
<proxy
autoDetect="false"
bypassonlocal="false"
proxyaddress="http://127.0.0.1:8888"
usesystemdefault="false" />
</defaultProxy>
</system.net>
Mocking and testing live responses
Instead of doing this, I highly recommend using a mockable proxy such as MockServer or running it in memory using an OWIN based hosted mocking server like JustFakeIt and running tests in memory.