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For years now, Active Server Pages (ASP) has been arguably the leading choice
for Web developers building dynamic Websites on Windows Web servers. ASP
has gained popularity by offering the simplicity of flexible scripting via several
languages. That, combined with the fact that it’s built into every Microsoft
Windows-based Web server, has made ASP a difficult act to follow.

Early in 2002, Microsoft released its new technology for Internet development.
Originally called ASP+, it was finally released as ASP.NET, and represents a leap
forward from ASP both in sophistication and productivity for the developer. It
continues to offer flexibility in terms of the languages it supports, but instead of
a range of simple scripting languages, developers can now choose between several
fully-fledged programming languages. Development in ASP.NET requires not
only an understanding of HTML and Web design, but also a firm grasp of the
concepts of object-oriented programming and development.

In the next few sections, I’ll introduce you to the basics of ASP.NET. I’ll walk
you through installing it on your Web server, and take you through a simple dynamic example that demonstrates how ASP.NET pages are constructed. First, let’s define what ASP.NET actually is.
ASP.NET is a server-side technology for developing Web applications based on the Microsoft .NET Framework. Let’s break that jargon-filled sentence down.

ASP.NET is server-side; that is, it runs on the Web server. Most Web designers start by learning client-side technologies like HTML, JavaScript, and Cascading Style Sheets (CSS). When a Web browser requests a Web page created with clientside technologies, the Web server simply grabs the files that the browser (the
client) requests and sends them down the line. The client is entirely responsible for reading the code in the files and interpreting it to display the page on the screen. Server-side technologies, like ASP.NET, are different. Instead of being interpreted by the client, server-side code (for example, the code in an ASP.NET page) is interpreted by the Web server. In the case of ASP.NET, the code in the page is read by the server and used dynamically to generate standard HTML/JavaScript/CSS that is then sent to the browser. As all processing of
ASP.NET code occurs on the server, it’s called a server-side technology. As Figure 1.1 shows, the user (client) only sees the HTML, JavaScript, and CSS within the browser. The server (and server-side technology) is entirely responsible for processing the dynamic portions of the page.
 
ASP.NET is a technology for developing Web applications. A Web application is just a fancy name for a dynamic Website. Web applications usually (but not always) store information in a database on the Web server, and allow visitors to the site to access and change that information. Many different programming technologies and supported languages have been developed to create Web applications; PHP, JSP (using Java), CGI (using Perl), and ColdFusion (using CFML) are just a few of the more popular ones. Rather than tying you to a specific technology and language, however, ASP.NET lets you write Web applications
using a variety of familiar programming languages. Finally, ASP.NET is based on the Microsoft .NET Framework. The .NET Framework collects all the technologies needed for building Windows applications,
Web applications, and Web Services into a single package with a set of more than twenty programming languages. To develop Websites with ASP.NET, you’ll need to download the .NET Framework Software Development Kit, which I’ll guide you through in the next few sections. Even with all the jargon demystified, you’re probably still wondering: what makes ASP.NET so good? Compared with other options for building Web applications, ASP.NET has the following advantages:
1.  ASP.NET lets you use your favorite programming language, or at least one that’s really close to it. The .NET Framework currently supports over twenty languages, four of which may be used to build ASP.NET Websites.
2. ASP.NET pages are compiled, not interpreted. Instead of reading and interpreting your code every time a dynamic page is requested, ASP.NET compiles dynamic pages into efficient binary files that the server can execute very quickly. This represents a big jump in performance when compared with the technology’s interpreted predecessor, ASP.
3. ASP.NET has full access to the functionality of the .NET Framework. Support for XML, Web Services, database interaction, email, regular expressions, and many other technologies are built right into .NET, which saves you from having to reinvent the wheel.
4. ASP.NET allows you to separate the server-side code in your pages from the HTML layout. When you’re working with a team composed of programmers and design specialists, this separation is a great help, as it lets programmers modify the server-side code without stepping on the designers’ carefully crafted HTML—and vice versa. With all these advantages, ASP.NET has relatively few downsides. In fact, only
two come to mind:
5.  ASP.NET is a Microsoft technology. While this isn’t a problem in itself, it does mean that, at least for now, you need to use a Windows server to run an ASP.NET Website. If your organization uses Linux or some other operating system for its Web servers, you’re out of luck.
6. Serious ASP.NET development requires an understanding of object-oriented programming, which we’ll cover over the next few chapters. Still with me? Great! It’s time to gather the tools and start building!