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Beginning ASP.NET 2.0 in C#

ASP (Active Server Pages) is a relatively new technology that’s already leapt through several stages of evolution. It was introduced about seven years ago as an easy way to add dynamic content to ordinary web pages. Since then, it’s grown into something much more ambitious: a platform for creating advanced web applications, including e.commerce shops, data.driven portal sites, and just about anything else you can find on the Internet.ASP.NET 2.0 is the latest version of ASP, and it represents the most dramatic change yet. With ASP.NET, developers no longer need to paste together a jumble of HTML and script code in order to program the Web. Instead, you can create full.scale web applications using nothing but code and a design tool such as Visual Studio 2008 The cost of all this innovation is the learning curve. Not only do you need to learn how to use an advanced design tool (Visual Studio) and a toolkit of objects (the .NET Framework), you also need to master a programming language such as C#.The Internet began in the late 1960s as an experiment. Its goal was to create a truly resilient information network—one that could withstand the loss of several computers without preventing the others from communicating. Driven by potential disaster scenarios (such as nuclear attack), the U.S. Department of Defense provided the initial funding. The early Internet was mostly limited to educational institutions and defense contractors. It flourished as a tool for academic collaboration, allowing researchers across the globe to share information. In the early 1990s, modems were created that could work over existing phone lines, and the Internet began to open up to commercial users. In

1993, the first HTML browser was created, and the Internet revolution began. It

……………………………装……………………………………订…………………………………线……………………………would be difficult to describe early websites as web applications. Instead, the first generation of websites often looked more like brochures, consisting mostly of fixed HTML pages that needed to be updated by hand. Basic HTML page is a little like a word.processing document—it contains formatted content that can be displayed on your computer, but it doesn’t actually do anything. The following example shows HTML at its simplest, with a document that contains a heading and single line of text: An HTML document has two types of content: the text and the tags that tell the browser how to format it. The tags are easily recognizable, because they occur inside angled brackets (< >). HTML defines tags for different levels of headings, paragraphs, hyperlinks, italic and bold formatting, horizontal lines, and so on. For example,

Some Text

tells the browser to display Some Text in the Heading 1 style, which uses a large, bold font. Figure 1.1 shows the simple HTML page in a browser.HTML 2.0 introduced the first seed of web programming with a technology called HTML forms. HTML forms expand HTML so that it includes not only formatting tags but also tags for graphical widgets, or controls. These controls include common ingredients such as drop.down lists, text boxes, and buttons. Here’s a sample web page created with HTML form controls:HTML forms allow web application developers to design standard input pages. When the user clicks the Submit button on the page shown in Figure 1.2, all the data in the input controls (in this case, the two check boxes) is patched together into one long string and sent to the web server. On the server side, a custom application receives and processes the data. Amazingly enough, the controls that were created for HTML forms more than ten years ago are still the basic foundation that you’ll use to

build dynamic ASP.NET pages! The difference is the type of application that

……………………………装……………………………………订…………………………………线……………………………runs on the server side. In the past, when the user clicked a button on a form page, the information might have been e.mailed to a set account or sent to an application on the server that used the challenging CGI (Common Gateway Interface) standard. Today, you’ll work with the much more capable and elegant ASP.NET platform. To understand why ASP.NET was created, it helps to understand the problems of other web development technologies. With the original CGI standard, for example, the web server must launch a completely separate instance of the application for each web request. If the website is popular, the web server must struggle under the weight of hundreds of separate copies of the application, eventually becoming a victim of its own successor counter this problem, Microsoft developed ISAPI (Internet Server Application Programming Interface), a higher.level programming model. ISAPI solved the performance problem but at the cost of significant complexity. Even after ISAPI developers master the tricky C++ programming language, they still lie awake at night worrying about confounding issues such as multithreading. ISAPI programming is definitely not for the fainthearted. SAPI never really went away. Instead, Microsoft used it to build higher.level develop.mint platforms, such as ASP and ASP.NET. Both of these technologies allow developers to program dynamic web pages without worrying about the low.level implementation details. For that reason, both platforms have become incredibly successful. The original ASP platform garnered a huge audience of nearly one million developers. When ASP.NET was first released, it generated even more interest as the centerpiece of the .NET Frame.work. In fact, ASP.NET 1.0 was enthusiastically put to work in dozens of large.scale commercial websites even when it was only in late beta.