ASP.NET is more than the next version of Active Server Pages (ASP); it is a unified Web development platform that provides the services necessary for developers to build enterprise-class Web applications. While ASP.NET is largely syntax compatible with ASP, it also provides a new programming model and infrastructure for more secure, scalable, and stable applications. You can feel free to augment your existing ASP applications by incrementally adding ASP.NET functionality to them.

ASP.NET is a compiled, .NET-based environment; you can author applications in any .NET compatible language, including Visual Basic .NET, C#, and JScript .NET. Additionally, the entire .NET Framework is available to any ASP.NET application. Developers can easily access the benefits of these technologies, which include the managed common language runtime environment, type safety, inheritance, and so on.

ASP.NET has been designed to work seamlessly with WYSIWYG HTML editors and other programming tools, including Microsoft Visual Studio .NET. Not only does this make Web development easier, but it also provides all the benefits that these tools have to offer, including a GUI that developers can use to drop server controls onto a Web page and fully integrated debugging support.

Developers can use Web Forms or XML Web services when creating an ASP.NET application, or combine these in any way they see fit. Each is supported by the same infrastructure that allows you to use authentication schemes, cache frequently used data, or customize your application's configuration, to name only a few possibilities.

The .NET Framework is designed to fulfill the following objectives:

• To provide a consistent object-oriented programming environment whether object code is stored and executed locally, executed locally but Internet-distributed, or executed remotely.
• To provide a code-execution environment that minimizes software deployment and versioning conflicts.
• To provide a code-execution environment that guarantees safe execution of code, including code created by an unknown or semi-trusted third party.
• To provide a code-execution environment that eliminates the performance problems of scripted or interpreted environments.
• To make the developer experience consistent across widely varying types of applications, such as Windows-based applications and Web-based applications.
• To build all communication on industry standards to ensure that code based on the .NET Framework can integrate with any other code.

The .NET Framework has two main components: the common language runtime and the .NET Framework class library. The common language runtime is the foundation of the .NET Framework. Runtime is just like an agent that manages code at execution time, providing core services such as memory management, thread management, and remoting, while also enforcing strict type safety and other forms of code accuracy that ensure security and robustness. In fact, the concept of code management is a fundamental principle of the runtime. Code that targets the runtime is known as managed code, while code that does not target the runtime is known as unmanaged code. The class library, the other main component of the .NET Framework, is a comprehensive, object-oriented collection of reusable types that you can use to develop applications ranging from traditional command-line or graphical user interface (GUI) applications to applications based on the latest innovations provided by ASP.NET, such as Web Forms and XML Web services.

The .NET Framework can be hosted by unmanaged components that load the common language runtime into their processes and initiate the execution of managed code, thereby creating a software environment that can exploit both managed and unmanaged features. The .NET Framework not only provides several runtime hosts, but also supports the development of third-party runtime hosts.

For example, ASP.NET hosts the runtime to provide a scalable, server-side environment for managed code. ASP.NET works directly with the runtime to enable ASP.NET applications and XML Web services

Internet Explorer is an example of an unmanaged application that hosts the runtime (in the form of a MIME type extension). Using Internet Explorer to host the runtime enables you to embed managed components or Windows Forms controls in HTML documents. Hosting the runtime in this way makes managed mobile code (similar to Microsoft® ActiveX controls) possible, but with significant improvements that only managed code can offer, such as semi-trusted execution and secure isolated file storage.

Features of the Common Language Runtime?

• The common language runtime manages memory, thread execution, code execution, code safety verification, compilation, and other system services. These features are intrinsic to the managed code that runs on the common language runtime.
• The runtime is designed for the software of the future.
• It also supports software of today and yesterday.
• Interoperability between managed and unmanaged code enables developers to continue to use necessary COM components and DLLs.
• The runtime is designed to enhance performance. Although the common language runtime provides many standard runtime services, managed code is never interpreted. A feature called just-in-time (JIT) compiling enables all managed code to run in the native machine language of the system on which it is executing.
• The memory manager removes the possibilities of fragmented memory and increases memory locality-of-reference to further increase performance.

.NET Framework Class Library

The .NET Framework collection classes implement a set of interfaces that programmer can use to develop his own collection classes. Your collection classes will blend seamlessly with the classes in the .NET Framework.

An object-oriented class library, the .NET Framework types enable programmer to accomplish a range of common programming tasks, including tasks such as string management, data collection, database connectivity, and file access. In addition to these common tasks, the class library includes types that support a variety of specialized development scenarios. For example, you can use the .NET Framework to develop the following types of applications and services:

• Console applications: Applications in the .NET framework can use the System.Console class to read characters from and write characters to the console. Data from the console is read from the standard input stream, data to the console is written to the standard output stream, and error data to the console is written to the standard error output stream. These streams are automatically associated with the console when the application starts and are presented as the In, Out, and Error properties, respectively.
• Windows GUI applications (Windows Forms): A form is a bit of screen real estate, usually rectangular, that you can use to present information to the user and to accept input from the user. Forms can be standard windows, multiple document interface (MDI) windows, dialog boxes, or display surfaces for graphical routines. The easiest way to define the user interface for a form is to place controls on its surface. Forms are objects that expose properties which define their appearance, methods which define their behavior, and events which define their interaction with the user. By setting the properties of the form and writing code to respond to its events, you customize the object to meet the requirements of your application.
• ASP.NET applications: An ASP.NET application is defined as all the files, pages, handlers, modules, and executable code that can be invoked from a virtual directory and its subdirectories on a Web application server. Programmer can use any of the ASP.NET programming models within any application programmer define, based on either Web Forms or XML Web services. They must coexist in a single virtual directory structure.
• XML Web services: An XML Web service is a programmable entity that provides a particular element of functionality, such as application logic, and is accessible to any number of potentially disparate systems using ubiquitous Internet standards, such as XML and HTTP. XML Web services depend heavily upon the broad acceptance of XML and other Internet standards to create an infrastructure that supports application interoperability at a level that solves many of the problems that previously hindered such attempts.