An HttpModule is a method of implementing and registering a class that can handle events generated by the HttpApplication class during the processing of a request. When an event is generated, the HttpModule can do additional processing on the request. HttpModules provide similar functionality to ISAPI filters, but are much easier to design and implement. Because an HttpModule is a global object, it is used to do things that affect most ”if not all ”of the .aspx files in your application. Here is a partial list of things that you can do with an HttpModule:
An HttpModule has two basic purposes. It provides event handlers for events that the Application object generates and can generate events that can be handled in your Global.asax file or the code file behind the Global.asax file. Both these purposes are discussed in detail in this chapter.