ASP.NET in a Nutshell

Stages of Page Processing

During Web Forms processing, the page goes through distinct stages, which are illustrated in Figure 3-1. The Web Forms processor calls a corresponding page processing event at each stage.

Figure 3-1. The stages of Web Forms page processing

In ASP pages other than global.asa, you have to write your program logic sequentially because your code is executed in the order in which it appears (termed procedural programming ). ASP.NET, on the other hand, features event-driven programming , in which the order of execution of a particular code block is not predetermined. You write a block of code called an event handler that is executed whenever that event occurs.

If you’ve developed client-side code or have programmed using Visual Basic, you’re already familiar with event-driven programming. ASP.NET takes event-driven programming to the server side, encouraging you to structure your programming logic into event handlers. In ASP.NET, the Page object is the representation of your ASP.NET page, and you can write handlers at the page level. ASP, on the other hand, supports only events at the application and session levels.

The Page class inherits all of its important events from the System.Web.UI.Control class, which is the ultimate parent of all server controls. This means that all events described below also apply to both built-in and custom server controls because ...