Web site applications can contain a number of file types, some supported and managed by ASP.NET, and others supported and managed by the IIS server.

Most of the ASP.NET file types can be automatically generated using the Add New Item menu item in Visual Web Developer.

File types are mapped to applications using application mappings. For example, if you open a file with the .txt file-name extension, the Notepad application will probably open, because .txt file types are mapped by default to Notepad.exe. In Web applications, file types are mapped to application extensions in IIS. For more information, see Setting Application Mappings in IIS Help.

File Types Managed by ASP.NET

File types that are managed by ASP.NET are mapped to the Aspnet_isapi.dll in IIS.

File type	Location	Description
.asax	Application root.	Typically a Global.asax file that contains code that derives from the HttpApplication class and represents the application. For more information, see Global.asax Syntax.
.ascx	Application root or a subdirectory.	A Web user control file that defines a custom, reusable user control. For more information, see ASP.NET User Controls.
.ashx	Application root or a subdirectory.	A generic handler file that contains code that implements the IHttpHandler interface to handle all incoming requests. For more information, see Introduction to HTTP Handlers.
.asmx	Application root or a subdirectory.	An XML Web Services file that contains classes and methods that will be available to other Web applications by way of SOAP. For more information, see XML Web Services Publishing and Deployment.
.aspx	Application root or a subdirectory.	An ASP.NET Web forms file that can contain Web controls and other business logic. For more information, see ASP.NET Web Pages and ASP.NET Web Server Controls.
.axd	Application root.	A trace-viewer file, typically Trace.axd. For more information, see ASP.NET Tracing.
.browser	App_Browsers subdirectory.	A browser definition file used to identify the enabled features of the client browser. For more information, see ASP.NET Web Server Controls and Browser Capabilities.
.cd	Application root or a subdirectory.	A class diagram file.
.compile	Bin subdirectory.	A precompiled stub file that points to the appropriate assembly. Executable file types (.aspx, ascx, .master, theme files) are precompiled and put in the Bin subdirectory. For more information, see ASP.NET Web Site Precompilation Overview.
.config	Application root or a subdirectory.	Typically a Web.config configuration file that contains XML elements whose settings configure the various features of ASP.NET. For more information, see ASP.NET Configuration Files.
.cs, .jsl, .vb	App_Code subdirectory, or in the case of a code-behind file for an ASP.NET page, in the same directory as the Web page.	Class source-code file that is compiled at run time. The class can be an HTTP Module, an HTTP Handler, or a code-behind file for an ASP.NET pageIntroduction to HTTP Handlers.
.csproj, .vbproj, vjsproj	Visual Studio project directory.	A project file for a Visual Studio client-application project.
.disco, .vsdisco	App_WebReferences subdirectory.	An XML Web Services Discovery file used to help locate available Web services. For more information, see XML Web Services Publishing and Deployment.
.dsdgm, .dsprototype	Application root or a subdirectory.	A distributed service diagram (DSD) file that can be added to any Visual Studio solution that provides or consumes Web services to reverse-engineer an architectural view of the Web service interactions. For more information, see XML Web Services Publishing and Deployment.
.dll	Bin subdirectory.	A compiled class library file. Alternatively, you can put source code for classes in the App_Code subdirectory. For more information, see Shared Code Folders in ASP.NET Web Sites.
.licx, .webinfo	Application root or a subdirectory.	A license file. Licensing allows control authors to help protect intellectual property by checking that a user is authorized to use the control. For more information, see How to: License Components and Controls.
.master	Application root or subdirectory.	A master page that defines the layout for other Web pages in the application that reference the master. For more information, see ASP.NET Master Pages.
.mdb, .ldb	App_Data subdirectory.	An Access database file. For more information, see Accessing Data with ASP.NET.
.mdf	App_Data subdirectory.	SQL database file. For more information, see Accessing Data with ASP.NET.
.msgx, .svc	Application root or a subdirectory.	An Indigo Messaging Framework (MFx) service file.
.rem	Application root or a subdirectory.	A remoting handler file. For more information, see SOAP Message Modification Using SOAP Extensions.
.resources	App_GlobalResources or App_LocalResources subdirectory.	A resource file that contains resource strings that refer to images, localizable text, or other data. For more information, see Resources in Applications or How to: Create Resource Files for ASP.NET Web Sites.
.resx	App_GlobalResources or App_LocalResources subdirectory.	A resource file that contains resource strings that refer to images, localizable text, or other data. For more information, see Resources in Applications or How to: Create Resource Files for ASP.NET Web Sites.
.sdm, .sdmDocument	Application root or a subdirectory.	A system definition model (SDM) file.
.sitemap	Application root.	A site-map file that contains the structure of the Web site. ASP.NET comes with a default site-map provider that uses site-map files to easily display a navigational control in a Web page. For more information, see ASP.NET Site Navigation.
.skin	App_Themes subdirectory.	A skin file used to determine display formatting. For more information, see ASP.NET Themes and Skins.
.sln	Visual Web Developer project directory.	A solution file for a Visual Web Developer project.
.soap	Application root or a subdirectory.	A SOAP extension file. For more information, see SOAP Message Modification Using SOAP Extensions.

File Types Managed by IIS

File types that are managed by ASP.NET are usually mapped to asp.dll in IIS.

File type

Location

Description

.asa

Application root.

Typically a Global.asa file that contains optional methods that run at the start or end of the ASP session or application lifetime.

For more information, see Global.asa Syntax in the IIS SDK.

.asp

Application root or a subdirectory.

An ASP Web page that contains @ directives and script code that uses the ASP built-in objects.

For more information, see IIS ASP Scripting Reference in the IIS SDK.

.cdx

App_Data subdirectory.

A compound index file structure file for Visual FoxPro.

For more information, see Compound Index File Structure in MSDN.

.cer

Application root or a subdirectory.

A certificate file used to authenticate a Web site.

For more information, see Certificates in the IIS Operations Guide.

.idc

Application root or a subdirectory.

An Internet Database Connector file mapped to httpodbc.dll.

Note
IDC has been deprecated because it does not provide enough security for data connections. IIS 6.0 will be the last version to include IDC.

.shtm, .shtml, .stm

Application root or a subdirectory.

Mapped to ssinc.dll.

For more information, see IIS Server-Side Include Directives in the IIS SDK.

Static File Types

IIS only serves static files with file-name extensions that are registered in the MIME types list. This list is stored in the MimeMap IIS metabase property for an application. If a file type is mapped to an application extension, it does not need to be included in the MIME types list unless you want the file to be treated like a static file. Typically, ASP.NET source code file types should not be in the MIME types list because that might allow browsers to view the source code.

The following table lists only a few of the registered file types.

File type	Location	Description
.css	Application root or subdirectory, or App_Themes subdirectory.	Style sheet files used to determine the formatting of HTML elements.
.htm, .html	Application root or subdirectory.	Static Web files written in HTML code.

File Types Managed by ASP.NET

File Types Managed by IIS

Static File Types

See Also

Concepts