The ASP.NET configuration system features an extensible infrastructure that enables you to define configuration settings at the time your ASP.NET applications are first deployed so that you can add or revise configuration settings at any time with minimal impact on operational Web applications and servers.
ASP.NET configuration data is stored in XML text files that are each named Web.config. Web.config files can appear in multiple directories in ASP.NET applications. These files allow you to easily edit configuration data before, during, or after applications are deployed on the server. You can create and edit ASP.NET configuration files by using standard text editors, the ASP.NET MMC snap-in, the Web Site Administration Tool, or the ASP.NET configuration API.
ASP.NET configuration files keep application configuration settings separate from application code. Keeping configuration data separate from code makes it easy for you to associate settings with applications, change settings as needed after deploying an application, and extend the configuration schema.
The ASP.NET configuration system provides the following benefits:
- Configuration information is stored in XML-based text files. You can use any standard text editor or XML parser to create and edit ASP.NET configuration files.
- Multiple configuration files, all named Web.config, can appear in multiple directories on an ASP.NET Web application server. Each Web.config file applies configuration settings to its own directory and all child directories below it. Configuration files in child directories can supply configuration information in addition to that inherited from parent directories, and the child directory configuration settings can override or modify settings defined in parent directories. The root configuration file named systemroot\Microsoft.NET\Framework\versionNumber\CONFIG\Machine.config provides ASP.NET configuration settings for the entire Web server.
- At run time, ASP.NET uses the configuration information provided by the Web.config files in a hierarchical virtual directory structure to compute a collection of configuration settings for each unique URL resource. The resulting configuration settings are then cached for all subsequent requests to a resource. Note that inheritance is defined by the incoming request path (the URL), not the file system paths to the resources on disk (the physical paths).
- ASP.NET detects changes to configuration files and automatically applies new configuration settings to Web resources affected by the changes. The server does not have to be rebooted for the changes to take effect. Hierarchical configuration settings are automatically recalculated and recached whenever a configuration file in the hierarchy is changed. The <processModel> section is an exception.
- The ASP.NET configuration system is extensible. You can define new configuration parameters and write configuration section handlers to process them.
- ASP.NET help protect configuration files from outside access by configuring Internet Information Services (IIS) to prevent direct browser access to configuration files. HTTP access error 403 (forbidden) is returned to any browser attempting to request a configuration file directly.