Each Web.config file applies configuration settings to the directory that it is in and to all of the child directories below it. Settings in child directories can optionally override or modify settings that are specified in parent directories. Configuration settings in a Web.config file can optionally be applied to individual files or subdirectories by specifying a path in a location element.

The root of the ASP.NET configuration hierarchy is the systemroot\Microsoft.NET\Framework\versionNumber\CONFIG\Web.config file, which includes settings that apply to all ASP.NET applications that run a specific version of the .NET Framework. Because each ASP.NET application inherits default configuration settings from the root Web.config file, you need to create Web.config files only for settings that override the default settings.

Note:
The root Web.config file inherits some basic configuration settings from the Machine.config file, which is located in the same directory. Some of these settings cannot be overridden in Web.config files. For more information, see ASP.NET Configuration File Hierarchy and Inheritance.

At run time, ASP.NET uses the Web.config files to hierarchically compute a unique collection of configuration settings for each incoming URL request. These settings are calculated only once and then cached on the server. ASP.NET detects any changes to the configuration files and then automatically applies those changes to the affected applications, restarting the applications in most cases. Hierarchical configuration settings are automatically calculated and cached again whenever a configuration file in the hierarchy is changed. The IIS server does not have to be restarted for the changes to take effect unless the processModel section has been changed.

For more information about how the ASP.NET configuration hierarchy works, see ASP.NET Configuration File Hierarchy and Inheritance and ASP.NET Configuration Scenarios.

You can use a text editor or an XML editor to edit the configuration files directly. For proper syntax, see the reference topics in the configuration sections in ASP.NET Configuration Settings and General Configuration Settings (ASP.NET). For more information, see Editing ASP.NET Configuration Files.

The Web.config file for an ASP.NET application that targets the .NET Framework version 3.5 contains configuration elements that are not found in the Web.config files for earlier versions. This expanded Web.config file is also created when you open an existing Web site in and upgrade the Web site to target the .NET Framework version 3.5. In that case, Visual Studio updates the application's Web.config file to include the additional configuration elements.

The following table shows the new configuration elements and the changes to configuration elements from earlier versions of the .NET Framework.

The Microsoft Management Console (MMC) snap-in for ASP.NET provides a convenient way to manipulate ASP.NET configuration settings at all levels on a local or remote Web server. The ASP.NET MMC snap-in uses the ASP.NET configuration API, but it simplifies the process of editing configuration settings by providing a graphical user interface (GUI). In addition, the tool supports the ASP.NET configuration API features that control whether settings can be inherited by Web applications, and manage the dependencies between levels of the configuration hierarchy.

Note:
To use the ASP.NET MMC snap-in, you must log on to the computer with an account that has administrative privileges.

The ASP.NET MMC snap-in appears as an ASP.NET tab on the property sheet of a virtual directory.

For more information, see MMC Snap-In for ASP.NET.

The Web Site Administration Tool allows anyone with administrative privileges for the Web site to manage the configuration settings for that Web site. The Web Site Administration Tool is designed to provide a user-friendly, graphical editing tool for the configuration settings that are most commonly used in individual Web sites. Because the tool uses a browser-based interface, it allows you to change Web site settings remotely, which is useful for administering a site that is already deployed to a production Web server, such as a hosted Web site.

The Web Site Administration Tool differs from the ASP.NET MMC snap-in in several ways. For instance, the ASP.NET MMC snap-in is ideal for administrator-level configuration because it provides access to the entire hierarchy of configuration files on the Web server instead of the configuration settings for a single Web site. Also, you must be an administrator to use the ASP.NET MMC snap-in, whereas the Web Site Administration Tool only allows individual Web site owners to configure the Web.config file in the root directory of sites to which they have administrative privileges. Finally, you cannot use the ASP.NET MMC snap-in to administer IIS remotely, but the browser interface for the Web Site Administration Tool allows remote configuration for versions of IIS beginning with IIS 6.0.

The Web Site Administration Tool includes a tabbed interface that groups related configuration settings on the following tabs:

• A Security tab, which contains settings to help secure Web-application resources and to manage user accounts and roles.

• A Profile tab, which contains settings to manage how visitor information is gathered by the Web site.

• An Application tab, which contains settings to manage configuration elements that affect ASP.NET applications.

• A Provider tab, which contains settings to add, edit, delete, test, or assign application providers.

The Web Site Administration Tool is automatically installed with the .NET Framework version 2.0 and later. For information about how the tool works, see ASP.NET Web Site Administration Tool.

The .NET Framework includes command-line tools that perform specific configuration operations. For example, the Aspnet_regiis.exe tool allows you to specify which version of the .NET Framework applies to your ASP.NET application. For more information, see .NET Framework Tools.