Route a request to a proxy server

Normally, in ASP.NET applications, we read from a Request object and write to the Response buffer.

However, I wish to read the request object, do some validations on it, and route the request to a proxy server. How is routing a request to a proxy server achieved in ASP.NET?

It's not achieved. The web is stateless and client-agnostic so you can't tell where the output stream should go.