.net页面对象模型要点.doc

外文资料原文 ASP.NET PAGE OBJECT MODEL Summary: Learn about the eventing model built around ASP.NET Web pages and the various stages that a Web page experiences on its way to HTML. The ASP.NET HTTP run time governs the pipeline of objects that transform the requested URL into a living instance of a page class first, and into plain HTML text next. Discover the events that characterize the lifecycle of a page and how control and page authors can intervene to alter the standard behavior. (6 printed pages) Introduction: Each request for a Microsoft? ASP.NET page that hits Microsoft? Internet Information Services (IIS) is handed over to the ASP.NET HTTP pipeline. The HTTP pipeline is a chain of managed objects that sequentially process the request and make the transition from a URL to plain HTML text happen. The entry point of the HTTP pipeline is the HttpRuntime class. The ASP.NET infrastructure creates one instance of this class per each AppDomain hosted within the worker process (remember that the worker process maintains one distinct AppDomain per each ASP.NET application currently running). The HttpRuntime class picks up an HttpApplication object from an internal pool and sets it to work on the request. The main task accomplished by the HTTP application manager is finding out the class that will actually handle the request. When the request is for an .aspx resource, the handler is a page handler—namely, an instance of a class that inherits from Page. The association between types of resources and types of handlers is stored in the configuration file of the application. More exactly, the default set of mappings is defined in the httpHandlers section of the machine.config file. However, the application can customize the list of its own HTTP handlers in the local web.config file. The line below illustrates the code that defines the HTTP handler for .aspx resources. add verb=* path=*.aspx type=System.Web.UI.PageHandlerFactory/ An extension can be associated with a handler cl