15.1 The Configuration Files

Each of the .NET configuration files shares a common XML format, although their scopes differ depending on which location the file is in. Some of the files are installed and configured automatically when the framework is installed.

Although the contents of the files differ, they share a common schema. The root element of each file is the configuration element, although different elements will appear as child nodes in the different files. Because the configuration files are all XML, you can deal with them as you would any XML document, including editing them with a text editor, or using the classes in the System.Xml namespace to manipulate them.

Although you can edit the configuration file as much as you want, be sure to note that you're just editing the file on disk. No changes you make on disk will affect the configuration settings once they've been read into the configuration system by a running application.

15.1.1 The Security Configuration Files

There are several different security policy configuration files: the enterprise security policy configuration file in %windir%\Microsoft.NET\Framework\v%version%\CONFIG\enterprisesec.config, the machine security policy configuration file in %windir%\Microsoft.NET\Framework\v%version%\CONFIG\security.config, and the user security policy configuration file in %userprofile%\Applicationdata\Microsoft\CLRsecurity config\v%version%\security.config (for Windows 2000 and Windows NT) or %windir%\username\CLRsecurityconfig\v%version%\security.config (for Windows 98 and Windows Me). There may also be web_hightrust.config, web_lowtrust.config, and web_notrust.config files in the %windir%\Microsoft.NET\Framework\v%version%\CONFIG directory.

The security policy files contain configuration settings that pertain to security for particular assemblies. It is strongly recommended that you do not edit these files directly, instead using the .NET Framework Configuration tool (mscorcfg.msc) or Code Access Security Policy tool (caspol.exe) to edit security policies. For more information on configuring .NET security policies, see .NET Framework Security by Brian A. LaMacchia, Sebastian Lange, Matthew Lyons, Rudi Martin, and Kevin T. Price (Addison Wesley).

15.1.2 The Machine Configuration File

The machine configuration file, located in %windir%\Microsoft.NET\Framework\v%version%\CONFIG\machine.config, contains configuration settings specific to the machine it is installed on. While most of these settings pertain to functionality internal to the .NET Framework, it may also be used to store configuration settings common to more than one application. If you do use it store shared application configuration settings, you should be careful to name your settings in a unique way. You should also take care not to disrupt any existing machine configuration settings when adding your own configuration settings to the machine configuration file.

Some of the settings in this file include debugging and error message configuration; network configuration, such as authentication details and web proxy location; a large number of ASP.NET configuration settings, including settings that let you specify how different web browser platforms and versions should be recognized; and remoting configuration. Many of the settings in the machine configuration file may also be configured at runtime for a particular application instance. However, changes to these settings at runtime do not persist in the machine configuration file, nor are they shared across different application instances.

15.1.3 The Application Configuration File

The application configuration file is the one configuration file that you have complete control over, and it is where you should put your application configuration settings. The application configuration file is automatically read when necessary, and it must be located in the same directory as the application, and named with the same name as the application executable plus the extension .config. If your application executable is named C:\MyApp.exe, for example, the application configuration file must be named C:\MyApp.exe.config.

In the next section, I'll describe how you can add your own settings to the machine or application configuration files.