ASP.NET
![]() | It has been suggested that ASP master pages be merged into this article. (Discuss) Proposed since December 2006. |
ASP.NET is a set of web application development technologies marketed by Microsoft. Programmers can use it to build dynamic web sites, web applications and XML web services. It is part of Microsoft's .NET platform and is the successor to Microsoft's Active Server Pages (ASP) technology.
ASP.NET is built on the Common Language Runtime, meaning programmers can write ASP.NET code using any Microsoft .NET language.
ASPX file format
ASPX is a text file format used to create Webform pages; in programming jargon, the ASPX file typically contains static HTML or XHTML markup, as well as markup defining Web Controls and Web User Controls where the developer places all the required static and dynamic content for the web page. Additionally, dynamic code which runs on the server can be placed in a page within a block <% -- dynamic code -- %>
which is similar to other web development technologies such as PHP, JSP, and ASP, but this practice is generally discouraged except for Databinding.
The recommended method for dealing with dynamic program code is to use the code-behind model, which places this code in a separate file or in a specially designated script tag. Code-behind files are typically named something to the effect of MyPage.aspx.cs or MyPage.aspx.vb based on the ASPX file name (this practice is automatic in Microsoft Visual Studio and other IDEs. When using this style of programming, the developer writes code to respond to different events, like the page being loaded, or a control being clicked, rather than a procedural walk through the document.
Other files
Other file extensions associated with different versions of ASP.NET include:
- ascx - Web UserControls: custom controls to be placed onto web pages.
- asmx - web service pages.
- ashx - custom HTTP handlers
- master - Master Pages; introduced in version 2.0
- sitemap - sitemap configuration files
- skin - theme skin files
- config - web.config is the only file to use this extension by default, however ASP.NET provides facilities to create and consume other config files. These are stored in XML format, so as to allow configuration changes to be made with simplicity.
Performance
ASP.NET aims for performance benefits over other script-based technologies ( including ASP Classic ) by compiling the server-side code to one or a few DLL files on the web server. This happens transparently in the background the first time a page is requested (i.e., the developer need not perform a separate compilation step for pages). This provides the ease of development offered by scripting languages with the performance benefits of a compiled binary.
The ASPX and other resource files are placed in a virtual host on an Internet Information Services ( or other compatible ASP.NET servers; see Other Implementations, below ). The first time a client requests a page, the .NET framework parses and compiles the file(s) into a .NET assembly and sends the response; subsequent requests are served from the dll files.
Developers can also choose to pre-compile their code before deployment, eliminating the need for just-in-time compilation in a production environment.
ASP.NET compared to ASP classic
ASP.NET attempts to simplify developers' transition from Windows application development to web development by offering the ability to build pages composed of controls similar to a Windows user interface. A web control, such as a button or label, functions in very much the same way as its Windows counterpart: code can assign it properties and respond to its events. Controls know how to render themselves: whereas Windows controls draw themselves to the screen, web controls produce segments of HTML and JavaScript which form part of the resulting page sent to the end-user's browser.
ASP.NET encourages the programmer to develop applications using an event-driven GUI paradigm (event-driven GUI model), rather than in conventional web-scripting environments like ASP and PHP. The framework attempts to combine existing technologies such as JavaScript with internal components like "ViewState" to bring persistent (inter-request) state to the inherently stateless web environment.
- Compiled code means applications run faster with more design-time errors trapped at the development stage.
- Significantly improved run-time error handling, making use of exceptions and try-catch blocks.
- Similar metaphors to Windows applications such as controls and events, which make development of rich user interfaces, previously only found on the desktop, possible.
- An extensive set of controls and class libraries allows the rapid building of applications, plus user-defined controls allow commonly used templates, such as menus.
- ASP.NET leverages the multi-language capabilities of the .NET CLR, allowing web pages to be coded in VB.NET, C#, J#, etc.
- Ability to cache the whole page or just parts of it to improve performance.
- Ability to use the code-behind development model to separate business logic from presentation.
- If an ASP.NET application leaks memory, the ASP.NET runtime unloads the AppDomain hosting the erring application and reloads the application in a new AppDomain.
- Session state in ASP.NET can be saved in a SQL Server database or in a separate process running on the same machine as the web server or on a different machine. That way session values are not lost when the web server is reset or the ASP.NET worker process is recycled.
- Previous versions of ASP.NET (1.0 and 1.1) were criticized for their lack of standards compliance. The generated HTML and JavaScript sent to the client browser would not always validate against W3C/ECMA standards. In addition, the framework's browser detection feature sometimes incorrectly identified web browsers other than Microsoft's own Internet Explorer as "downlevel" and returned HTML/JavaScript to these clients that was crippled or broken. However, in version 2.0, all controls generate valid HTML 4.0, XHTML 1.0 (the default) or XHTML 1.1 output, depending on the site configuration. Detection of standards-compliant web browsers is more robust and support for Cascading Style Sheets is more extensive.
Criticisms of ASP.NET
ASP Classic and ASP.NET can be run side-by-side in the same web application, which allows developers to migrate applications as needed, instead of all at once. Unfortunately, pages written using different versions of the ASP framework can't share Session State without a lot of work on the programmer's part, or the use of third-party libraries.
Unhandled exceptions force the ASP.NET worker processes to shut down - a fresh WP is loaded and the application is restarted. This causes the application to lose all data cached in session state and elsewhere; if the application authenticates users, they will be logged out. This type of error can be very difficult to debug in a large application.
ASP.NET 2.0 produces markup that passes W3C validation, but it is debatable as to whether this increases accessibility, one of the benefits of a semantic xhtml page + css representation. Several controls (eg. the Login controls, the Wizard control) use html tables for layout by default. ( Microsoft has now gone some way to solve this problem by releasing the ASP.NET 2.0 CSS Control Adapters, a free add-on that produces compliant accessible xhtml+css markup. ) However, some controls still rely on JavaScript. The CSS Control Adapters do help override output, even if it is to improve HTML, not CSS.
Development tools
Several available software packages exist for developing ASP.NET applications:
- Visual Studio .NET or Visual Studio 2005 or Visual Web Developer 2005 Express Edition (for ASP.NET 2.0)
- ASP.NET Web Matrix
- Macromedia Dreamweaver MX 2004 or Macromedia Dreamweaver 8
- Macromedia HomeSite 5.5 (For ASP Tags)
- Microsoft SharePoint Designer 12
- Delphi 2006
- SharpDevelop (Free/Open Source)
- Any text editor such as Notepad, Notepad++, UltraEdit, and myriad others.
History
Date | Version | Remarks | New features |
---|---|---|---|
January 16, 2002 | 1.0 | First version released together with Visual Studio .NET |
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April 24, 2003 | 1.1 | released together with Windows Server 2003 released together with Visual Studio .NET 2003 |
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November 7, 2005 | 2.0 |
codename Whidbey |
|
ASP.NET team members
Various ASP.NET team members maintain blogs. Here are some of them:
- Scott Guthrie, General Manager - http://weblogs.asp.net/scottgu
- Nikhil Kothari, Architect - http://www.nikhilk.net
- Brian Goldfarb, Product Manager - http://blogs.msdn.com/bgold
- Shanku Niyogi, Product Unit Manager - http://www.shankun.com
- Bertrand Le Roy, Developer - http://weblogs.asp.net/bleroy
See also
- Active Server Pages (ASP) – ASP.NET's predecessor
- ASP master pages
- Yellow Screen of Death – ASP.NET's Exception page
- Java Server Faces (JSF) – web application technology with a similar component based approach for the Java plattform
Resources about ASP.NET
- Pro ASP.NET 2.0 in C# 2005, Matthew MacDonald, Apress, November 27, 2005. ISBN 1-59059-496-7
- ASP.NET 2.0 Unleashed, Stephen Walther, Sams Publishing, June 6, 2006. ISBN 0-672-32823-2
- Essential ASP.NET With Examples in C#, Fritz Onion, Addison-Wesley Professional, February 11, 2003. ISBN 0-201-76040-1
- Programming ASP.NET, Jessy Liberty & Dan Hurwitz, O'Reilly, October, 2005. ISBN 0-596-00916-X
External links
![](http://upload.wikimedia.org/wikipedia/commons/thumb/d/df/Wikibooks-logo-en-noslogan.svg/40px-Wikibooks-logo-en-noslogan.svg.png)
Microsoft
- Microsoft's ASP.NET website
- ASP.NET on MSDN
- CSS friendly ASP.NET 2.0 control adapters
- Visual Web Developer Express Edition 2005
- Microsoft Expression Web Designer (Standards-compliant css-based design)
- Webmatrix for ASP.NET
Other implementations
- Mono - An open source .NET Framework implementation that runs on many platforms
- UltiDev Cassini Web Server - A free web server that can be redistributed with ASP.NET 1.1 and 2.0 applications