Introduction to ASP.NET

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 that enables a powerful new class of 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, C# and Jscript.NET. Additionally, the entire .NET Framework platform is available to any ASP.NET application. Developers can easily access the benefits of these technologies, which include a 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, as well as fully integrated debugging support.

Generally, developers choose from two programming models when creating an ASP.NET application, and combine them in any way they see fit.

• Web Forms allows you to build powerful forms-based Web pages. When building these pages, you can use Web Forms Controls to create common UI elements and program them for common tasks. These controls allow you to rapidly build up a Web Form out of reusable built-in or custom components, simplifying the code of a page.

• A Web service is a way to access server functionality remotely. Using services, businesses can expose programmatic interfaces to their data or business logic, which in turn can be obtained and manipulated by client and server applications. Web services enable the exchange of data in client-server or server-server scenarios, using standards like HTTP and XML messaging to move data across firewalls. Web services are not tied to a particular component technology or object-calling convention. As a result, programs written in any language, using any component model, and running on any operating system can access Web services.

Both of these options can take full advantage of all ASP.NET features, as well as the power of the .NET Framework and .NET Framework Common Language Runtime.

• ASP.NET not only takes advantage of performance enhancements found in the .NET Framework and runtime, it has also been designed to offer significant performance improvements over ASP and other Web development platforms. All ASP.NET code is compiled rather than interpreted, which allows early binding, strong typing, and just-in-time (JIT) compiling to native code, to name only a few of its benefits. ASP.NET is also easily factorable, meaning that developers can remove modules (a session module, for instance) that are not relevant to the application being developed. ASP.NET also provides extensive caching services, both built-in and caching APIs. ASP.NET also ships with Performance Counters that developers and system administrators can monitor to test new applications and gather metrics on existing ones.

• ASP.NET configuration settings are stored in XML-based files, which are human readable and writable. Each of your applications can have a distinct configuration file and you can extend the configuration scheme to suit your requirements.

• ASP.NET provides easy-to-use Application and Session state facilities that are familiar to ASP developers and are readily compatible with all other .NET Framework APIs.
  The .NET Framework and ASP.NET provide default authorization and authentication schemes for Web applications. You can easily remove, add to, or replace these schemes depending upon the needs of your application.

• Accessing databases from ASP.NET applications is an often-used technique for displaying data to Web site visitors. ASP.NET makes it easier than ever to access databases for this purpose - and provides for managing the data in the database.

• ASP.NET provides a simple framework that enables Web developers to write logic that runs at the application level. Developers can write this code in either the global.asax text file or in a compiled class deployed as an assembly. This logic can include application-level events, but developers can easily extend this framework to suit the needs of their Web application. ASP application code, written in the global.asa file, is completely supported in ASP.NET. You can simply rename global.asa to global.asax when upgrading from ASP.

• ASP.NET offers complete syntax and processing compatibility with ASP applications. Developers simply need to change file extensions from .asp to .aspx to migrate their files to the ASP.NET framework. They can also easily add ASP.NET functionality to their applications with ease, sometimes by simply adding just a few lines of code to their ASP files.