Applied XML Programming for Microsoft .NET.pdf - Csbdu.in

Chapter 15: .NET Framework ApplicationConfigurationOverviewTo the extent that it is possible, all applications, regardless of platform, should bedesigned in a parametric way and should read some of their settings from an externalfile. Simply by updating the configuration file, developers and system administrators canchange the way in which the application works as well as elements of the userinterface. In Microsoft Windows 3.x, user preferences and application settings wereusually stored in INI files located in the Windows folder or in the application's maindirectory. This practice was retained in Microsoft Win32, although since Windows 95,the system registry has become the recommended store for Win32 and ComponentObject Model (COM) application settings. With both INI files and the registry, however,the developer had a certain degree of freedom in designing the layout of the data.Various guidelines have been suggested over time, but in fact the structure of INI filesand registry subtrees was different from one application to the next.The Microsoft .NET Framework defines a tailor-made, XML-based API to accessconfiguration files and, in doing so, forces developers to adopt a common, rich, andpredefined schema for storing application settings. Using configuration files,administrators can control which resources a user can access, which versions ofassemblies an application will use and from where, and which connection stringsshould be used. Configuration files can also include application-specific settings suchas the buttons to be displayed on the toolbar, the size and position of controls, andother, more specific, state information. Using configuration files, you give yourapplication a bunch of dynamic properties and eliminate the need to recompile everytime different settings should be applied..NET Framework configuration files are XML files saved with the .config extension andnamed and located according to the type of the application. Managed code can use theclasses in the System.Configuration namespace to read settings from the configurationfiles but not to write settings to those files. Configuration files are considered plain XMLfiles, and appropriate XML writers should be used to edit their contents.In this chapter, we'll delve into the .NET Framework configuration engine, reviewing thecharacteristics of the main classes involved and how key tasks are accomplished. We'llanalyze the various types of configuration files and their overall schemas, and you'lllearn how to customize a .config file with custom tags and custom contents.Configuration FilesThe .NET Framework provides three basic types of configuration files: machine,application, and security. Despite their different contents and goals, all configurationfiles are XML files and share the same schema. For example, all configuration filesbegin with a node and then differentiate their contents and child nodesaccording to the final goal and the information contained. In this chapter, we'll focusprimarily on application configuration files, but this section also provides a quickintroduction to the other types of configuration files.504