Asp.Net – Introduction
Asp.net is the new offering for Web developers form the Microsoft. It is not simply the next generation of ASP. Because it has evolved from Asp, Asp.Net looks very similar to its predecessor. But concepts like web forms, Web Services, or server controls gives Asp.Net the power to build real Web application.
What is ASP.NET?
- ASP.NET provides services to allow the creation, deployment, and execution of Web Applications and Web Services
- Like ASP, ASP.NET is a server-side technology
- Web Applications are built using Web Forms. ASP.NET comes with built-in Web Forms controls, which are responsible for generating the user interface. They mirror typical HTML widgets like text boxes or buttons. If these controls do not fit your needs, you are free to create your own user controls.
- Web Forms are designed to make building web-based applications as easy as building Visual Basic applications
Features of ASP.NET.
- Separation of Code from HTML
To make a clean sweep, with ASP.NET you have the ability to completely separate layout and business logic. This makes it much easier for teams of programmers and designers to collaborate efficiently. This makes it much easier for teams of programmers and designers to collaborate efficiently.
- Support for compiled languages
developer can use VB.NET and access features such as strong typing and object-oriented programming. Using compiled languages also means that ASP.NET pages do not suffer the performance penalties associated with interpreted code. ASP.NET pages are precompiled to byte-code and Just In Time (JIT) compiled when first requested. Subsequent requests are directed to the fully compiled code, which is cached until the source changes.
- Use services provided by the .NET Framework The .NET Framework provides class libraries that can be used by your application. Some of the key classes help you with input/output, access to operating system services, data access, or even debugging. We will go into more detail on some of them in this module.
- Graphical Development Environment Visual Studio .NET provides a very rich development environment for Web developers. You can drag and drop controls and set properties the way you do in Visual Basic 6. And you have full IntelliSense support, not only for your code, but also for HTML and XML.
- State management To refer to the problems mentioned before, ASP.NET provides solutions for session and application state management. State information can, for example, be kept in memory or stored in a database. It can be shared across Web farms, and state information can be recovered, even if the server fails or the connection breaks down
- Update files while the server is running Components of your application can be updated while the server is online and clients are connected. The Framework will use the new files as soon as they are copied to the application. Removed or old files that are still in use are kept in memory until the clients have finished.
- XML-Based Configuration Files Configuration settings in ASP.NET are stored in XML files that you can easily read and edit. You can also easily copy these to another server, along with the other files that comprise your application.
Structure of Asp.Net
You can use directives to specify optional settings used by the page compiler when processing ASP.NET files. For each directive you can set different attributes. One example is the language directive at the beginning of a page defining the default programming language.
Code Declaration Blocks
Code declaration blocks are lines of code enclosed in <script> tags. They contain the runat=server attribute, which tells ASP.NET that these controls can be accessed on the server and on the client. Optionally you can specify the language for the block. The code block itself consists of the definition of member variables and methods.
Code Render Blocks
Render blocks contain inline code or inline expressions enclosed by the character sequences shown here. The language used inside those blocks could be specified through a directive like the one shown before.
HTML Control Syntax
You can declare several standard HTML elements as HTML server controls. Use the element as you are familiar with in HTML and add the attribute runat=server. This causes the HTML element to be treated as a server control. It is now programmatically accessible by using a unique ID. HTML server controls must reside within a <form> section that also has the attribute runat=server.
Custom Control Syntax
There are two different kinds of custom controls. On the one hand there are the controls that ship with .NET, and on the other hand you can create your own custom controls. Using custom server controls is the best way to encapsulate common programmatic functionality. Just specify elements as you did with HTML elements, but add a tag prefix, which is an alias for the fully qualified namespace of the control. Again you must include the runat=server attribute. If you want to get programmatic access to the control, just add an Id attribute.You can include properties for each server control to characterize its behavior. For example, you can set the maximum length of a TextBox. Those properties might have sub properties; you know this principle from HTML. Now you have the ability to specify, for example, the size and type of the font you use .The last attribute is dedicated to event binding. This can be used to bind the control to a specific event
Data Binding Expression
You can create bindings between server controls and data sources. The data binding expression is enclosed by the character sequences <%# and %>. The data-binding model provided by ASP.NET is hierarchical. That means you can create bindings between server control properties and superior data sources.
Server-side Object Tags
If you need to create an instance of an object on the server, use server-side object tags. When the page is compiled, an instance of the specified object is created. To specify the object use the identifier attribute. You can declare .NET objects using class as the identifier, and COM objects using either progid or classid.
Server-side Include Directives
With server-side include directives you can include raw contents of a file anywhere in your ASP.NET file. Specify the type of the path to filename with the pathtype attribute. Use either File, when specifying a relative path, or Virtual, when using a full virtual path.
To prevent server code from executing, use these character sequences to comment it out. You can comment out full blocks – not just single lines