【正文】 s Load event is triggered. You can add application logic to the page that executes whenever the Load event occurs. 2. Building Forms with Web Server Controls Building Smart Forms You use several of the basic Web controls to represent standard HTML form elements such as radio buttons, text boxes, and list boxes. You can use these controls in your pages to create the user interface for your Web application. The following sections provide detailed overviews and programming samples for each of these Web controls. Controlling Page Navigation In the following sections, you learn how to control how a user moves from one page to another. First, you learn how to submit an HTML form to another page and retrieve form information. Next, you learn how to use the Redirect() method to automatically transfer a user to a new page. Finally, you learn how to link pages together with the HyperLink control. Applying Formatting to Controls In the following sections, you learn how to make more attractive Web forms. First, you look at an overview of the formatting properties mon to all Web controls。t worry. Since VBScript is so closely related to Visual Basic, you39。t it be easier to create all this functionality once and use it for every language? The .NET Framework Class Library does exactly that. It consists of a vast set of classes designed to satisfy any conceivable programming need. For example, the .NET framework contains classes for handling database access, working with the file system, manipulating text, and generating graphics. In addition, it contains more specialized classes for performing tasks such as working with regular expressions and handling work protocols. The .NET framework, furthermore, contains classes that represent all the basic variable data types such as strings, integers, bytes, characters, and arrays. Most importantly, for purposes of this book, the .NET Framework Class Library contains classes for building pages. You need to understand, however, that you can access any of the .NET framework classes when you are building your pages. Understanding Namespaces As you might guess, the .NET framework is huge. It contains thousands of classes (over 3,400). Fortunately, the classes are not simply jumbled together. The classes of the .NET framework are anized into a hierarchy of namespaces. ASP Classic Note In previous versions of Active Server Pages, you had access to only five standard classes (the Response, Request, Session, Application, and Server objects). , in contrast, provides you with access to over 3,400 classes! A namespace is a logical grouping of classes. For example, all the classes that relate to working with the file system are gathered together into the namespace. The namespaces are anized into a hierarchy (a logical tree). At the root of the tree is the System namespace. This namespace contains all the classes for the base data types, such as strings and arrays. It also contains classes for working with random numbers and dates and times. You can uniquely identify any class in the .NET framework by using the full namespace of the class. For example, to uniquely refer to the class that represents a file system file (the File class), you would use the following: refers to the namespace, and File refers to the particular class. NOTE You can view all the namespaces of the standard classes in the .NET Framework Class Library by viewing the Reference Documentation for the .NET Framework. Standard Namespaces The classes contained in a select number of namespaces are available in your pages by default. (You must explicitly import other namespaces.) These default namespaces contain classes that you use most often in your applications: System— Contains all the base data types and other useful classes such as those related to generating random numbers and working with dates and times. — Contains classes for working with standard collection types such as hash tables, and array lists. — Contains classes that represent specialized collections such as linked lists and string collections. — Contains classes for working with configuration files ( files). — Contains classes for encoding, decoding, and manipulating the contents of strings. — Contains classes for performing regular expression match and replace operations. — Contains the basic classes for working with the World Wide Web, including classes for representing browser requests and server responses. — Contains classes used for caching the content of pages and classes for performing custom caching operations. — Contains classes for implementing authentication and authorization such as Forms and Passport authentication. — Contains classes for implementing session state. — Contains the basic classes used in building the user interface of pages. — Contains the classes for the HTML controls. — Contains the classes for the Web controls. .NET FrameworkCompatible Languages For purposes of this book, you will write the application logic for your pages using Visual Basic as your programming language. It is the default language for pages. Although you stick to Visual Basic in this book, you also need to understand that you can create pages by using any language that supports the .NET Common Language Runtime. Out of the box, this includes C, , and the Managed Extensions to C++. NOTE The CD included with this book contains C versions of all the code samples. Dozens of other languages created by panies other than Microsoft have been developed to work with the .NET framework. Some examples of these other languages include Python, SmallTalk, Eiffel, and COBOL. This means that you could, if you really wanted to, write pages using COBOL. Regardless of the language that you use to develop your pages, you need to understand that pages are piled before the