Add an HTTP Header with an HttpModule

An HttpModule is a perfect way to add an HTTP header to every request in IIS. An HttpModule is an assembly that is called on every request (and as of IIS 7 this includes non-ASPNET requests). Other uses of HttpModules include tracing, logging, and security. We have a change coming up where having an HTTP header added to certain responses will be very helpful. I thought I would share my C# code for the HttpModule and some JavaScript that will use the new HTTP header on the client to display a message.