Beginning Web Development, Silverlight, and ASP.NET AJAX

CHAPTER 3
Web Forms with ASP.NET
At the heart of web applications and web sites in ASP.NET are the elements that you use
to build the pages that the user will see. These are called web forms, terminology that is a
holdover from Windows development when windows were built using forms.
This methodology is unique and innovative in web development. It enables you to
create your pages in a visual manner, using server-side controls (as you saw in Chapter 2)
that are converted into HTML markup by the ASP.NET runtime at the time they are
served to the client. This chapter will go into some detail about web forms and how they
work in ASP.NET. You’ll learn about the event model of a page, and how postbacks work.
This chapter will also show you the life cycle of a page, and it will go into the object
model that the page supports, going through the control tree that ASP.NET exposes to
you as a developer. Finally, you’ll take an in-depth look at the Page class, and how it can
be used to control the flow between the server and your users, enabling you to access the
request and response streams, and parse and/or override them as necessary.
By the end of the chapter, you’ll have a good understanding of how web forms work,
and how you can use them to add great power to your web applications.
Understanding Page Processing
It is important to understand that there are a number of major differences between
building web applications and building standard Windows client applications. If you are
coming to web development from a Windows client development background, there are
several aspects of web development that are significantly different from Windows client
application development. Most Windows applications are designed to work with a single
user, but web applications that don’t scale to thousands of users are considered a failure.
Also, the application from a user’s perspective executes in a web browser, so local file system
permissions and system access is very limited. And perhaps the hardest concept to
grasp if you’re used to virtually unlimited memory and computational horsepower is that
web applications are by and large stateless, meaning that information isn’t retained on
the server between page invocations. (There are techniques to bypass this obstacle, but
even those require some design thought.)
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