The Pipeline Object Model

The Pipeline Object Model

The types defined in the System.Web namespace process HTTP requests using a pipeline model. The HTTP requests are passed to an instance of the HttpRuntime class, which represents the beginning of the pipe. The HttpRuntime object examines the request and figures out which application it was sent to (from the pipeline's perspective, a virtual directory is an application). Then it uses an HttpApplicationFactory to either find or create an HttpApplication object to process the request.

 An HttpApplication holds a collection of HTTP module objects, implementations of the IHttpModule interface. HTTP modules are filters that can examine and modify the contents of HTTP request and response messages as they pass through the pipeline. The HttpApplication object uses an HTTP handler factory to either find or create an HTTP handler object. HTTP handlers are endpoints for HTTP communication that process request messages and generate corresponding response messages. HTTP handlers and handler factories implement the IHttpHandler and IHttpHandlerFactory interfaces, respectively.