How ASP.NET Web Pages are Processed on the Web Server

Have you ever wondered, precisely, what happens on the Web server when a request for an ASP.NET Web page comes in?How does the Web server handle the incoming request? How is the HTML that is emitted to the client generated?What mechanisms are possible for us developers to work with an incoming request in its various stages of processing?In this article we'll take a rather detailed look at how ASP.NET Web pages are processed on the Web server.

Step 0: The Browser Makes an HTTP Request for an ASP.NET Web Page
The entire process begins with a Web browser making a request for an ASP.NET Web page. For example, a user mighttype into their browser's Address window the URL for this article, http://aspnet.4guysfromrolla.com/articles/011404.aspx.The Web browser, then, would make an HTTP request to the 4Guys Web server, asking for the particular file/articles/011404-1.aspx.

Step 1: The Web Server Receives the HTTP Request
The sole task of a Web server is to accept incoming HTTP requests and to return the requested resource in an HTTP response.The 4Guys Web server runs Microsoft's Internet Information Services (IIS) Web server. The first things IIS does whena request comes in is decide how to handle the request. Its decision is based upon the requested file's extension.For example, if the requested file has the .asp extension, IIS will route the request to be handled byasp.dll.

There are numerous file extensions that map to the ASP.NET engine, some of which include:

• .aspx, for ASP.NET Web pages,
• .asmx, for ASP.NET Web services,
• .config, for ASP.NET configuration files,
• .ashx, for custom ASP.NET HTTP handlers,
• .rem, for remoting resources
,
• And others!