IIS 6.0 with Windows Server 2003 added support for an
ISAPI feature called "wildcard mappings". Wildcard
mappings provide a way to configure IIS to cause all requests coming into the
server to first be routed to one or more ISAPI extensions for processing.
What is cool about wildcard mappings in IIS 6.0 is that after the ISAPI
extension that is processing the wildcard extension is finished, it can
then cause IIS to pass control of the request to the extension or internal
handler within IIS that normally would process the request.
ASP.NET 2.0 includes built-in support to take advantage of
this wildcard mapping feature. This enables you to run ASP.NET
code (or your own custom code) before and after the existing ISAPI
extension that processes a non-ASP.NET URL (for example: a .asp, .php or .htm
We can use this feature to enable a bunch of cool
integration features - including using ASP.NET authentication and authorization
features to secure all URLs on a web-server.