I'm working on a project where under certain circumstances (which can be identified either by the page the user came from or the value of a session variable) I need to add authentication information to the http headers in the request sent by the client (the application uses basic authentication so I just need to add the "Authorization: Basic <base64 string>" header. I think I should be able to do this using an HttpModule and the BeginRequest or some other event in the HttpApplication, but it seems that the HttpApplication's Request.Headers collection is always read-only. Am I right that I should be able to add a header using an HttpModule, and if so, can anybody offer an example to demonstrate how?