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ASP.NET and the .NET Framework ASP.NET is part of Microsoft's overall .NET framework, which contains a vast set of programming classes designed to satisfy any conceivable programming need.40838
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The .NET Framework Class Library
Imagine that you are Microsoft. Imagine that you have to support multiple programming languages—such as Visual Basic, JScript, and C++. A great deal of the functionality of these programming languages overlaps. For example, for each language, you would have to include methods for accessing the file system, working with databases, and manipulating strings.
Furthermore, these languages contain similar programming constructs. Every language, for example, can represent loops and conditionals. Even though the syntax of a conditional written in Visual Basic differs from the syntax of a conditional written in C++, the programming function is the same.
Finally, most programming languages have similar variable data types. In most languages, you have some means of representing strings and integers, for example. The maximum and minimum size of an integer might depend on the language, but the basic data type is the same.
Maintaining all this functionality for multiple languages requires a lot of work. Why keep reinventing the wheel? Wouldn'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 network protocols.
The .NET framework, furthermore, contains classes that represent all the basic variable data types such as strings, integers, bytes, characters, and arrays.
You need to understand, however, that you can access any of the .NET framework classes when you are building your ASP.NET 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 organized into a hierarchy of namespaces.
ASP Classic Note
The namespaces are organized 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:
System.IO.File
NOTE
Microsoft includes an interesting tool named the IL Disassembler (ILDASM) with the .NET framework. You can use this tool to view the disassembled code for any of the ASP.NET classes in the Temporary ASP.NET Files directory. It lists all the methods and properties of the class and enables you to view the intermediate-level code.
This tool also works with all the ASP.NET controls discussed in this chapter.
Introducing ASP.NET Controls
ASP.NET controls provide the dynamic and interactive portions of the user interface for your Web application. The controls render the content that the users of your Web site actually see and interact with. For example, you can use controls to create HTML form elements, interactive calendars, and rotating banner advertisements.
ASP.NET controls coexist peacefully with HTML content. Typically, you create the static areas of your Web pages with normal HTML content and create the dynamic or interactive portions with ASP.NET controls.
Adding Application Logic to an ASP.NET Page
The second building block of an ASP.NET page is the application logic, which is the actual programming code in the page.