File extensions in ASP.Net

File extensions associated with different versions of ASP.NET include:

.asax : Global.asax, used for application-level logic

.ascx : Web UserControls: custom controls to be placed onto web pages.

.ashx : custom HTTP handlers.

.asmx : web service pages. From version 2.0 a Code behind page of an asmx file is placed into the app_code folder.

.axd : when enabled in web.config requesting trace.axd outputs application-level tracing. Also used for the special webresource.axd handler which allows control/component developers to package a component/control complete with images, script, css etc. for deployment in a single file (an 'assembly')

.config : web.config is the only file in a specific Web application to use this extension by default (machine.config similarly affects the entire Web server and all applications on it), however ASP.NET provides facilities to create and consume other config files. These are stored in XML format.

.cs/vb : Code files (cs indicates C#, vb indicates Visual Basic). Code behind files (see above) predominantly have the extension ".aspx.cs" or ".aspx.vb" for the two most common languages. Other code files (often containing common "library" classes) can also exist in the web folders with the cs/vb extension. In ASP.NET 2 these should be placed inside the App_Code folder where they are dynamically compiled and available to the whole application.

.dbml : LINQ to SQL data classes file

.master : 2.0 master page file

.resx : resource files for internationalization and localization. Resource files can be global (e.g. messages) or "local" which means specific for a single aspx or ascx file.

.sitemap : sitemap configuration files. Default file name is web.sitemap

.skin : theme skin files.

.svc : Windows Communication Foundation service file

browser : browser capabilities files stored in XML format; introduced in version 2.0. ASP.NET 2 includes many of these by default, to support common web browsers. These specify which browsers have which capabilities, so that ASP.NET 2 can automatically customize and optimize its output accordingly. Special .browser files are available for free download to handle, for instance, the W3C Validator, so that it properly shows standards-compliant pages as being standards-compliant. Replaces the harder-to-use BrowserCaps section that was in machine.config and could be overridden in web.config in ASP.NET 1.x.