Professional ASP.NET 3.5 SP1 Edition: In C# and VB

Chapter 27. Modules and Handlers

Sometimes, just creating dynamic Web pages with the latest languages and databases does not give you, the developer, enough control over an application. At times, you need to be able to dig deeper and create applications that can interact with the Web server itself. You want to be able to interact with the low-level processes, such as how the Web server processes incoming and outgoing HTTP requests.

Before ASP.NET, to get this level of control using IIS, you were forced to create ISAPI extensions or filters. This proved to be quite a daunting and painful task for many developers because creating ISAPI extensions and filters required knowledge of C/C++ and knowledge of how to create native Win32 DLLs. Thankfully, in the .NET world, creating these types of low-level applications is really no more difficult than most other tasks you would normally perform. This chapter looks at two methods of manipulating how ASP.NET processes HTTP requests, the HttpModule, and the HttpHandler. Each method provides a unique level of access to the underlying processing of ASP.NET and can be a powerful tool for creating Web applications.

Processing HTTP Requests

Before starting to write Handlers or Modules, it's helpful to know how IIS and ASP.NET normally process incoming HTTP requests and what options you have for plugging custom logic into those requests. IIS is the basic endpoint for incoming HTTP requests. At a very high level, its job is to listen for and validate ...