.NET & XML

Using the appSettings Element

The easiest way to add configuration settings to a configuration file is to use the appSettings element. Configuration settings added this way take the form of key-value pairs. These key-value pairs may be added anywhere in the hierarchy of configuration files. Once added, key-value pairs can be removed individually in a configuration file lower in the hierarchy, or the entire set can be cleared.

Example 15-1 shows an excerpt from a machine configuration file, with an appSettings element added.

Example 15-1. Excerpt from the machine configuration file

<?xml version="1.0" encoding="UTF-8" ?>

<configuration>
  ...
  <appSettings>
    <add key="some key" value="some value" /> 
  </appSettings>
  ...
</configuration>

This configuration file simply adds a configuration setting whose key is “some key” and whose value is “some value”. The added key will be available to all .NET applications running on this machine.

Example 15-2 shows an application configuration file that uses the appSettings element to remove the key added in the machine configuration file and add another key.

Example 15-2. The application configuration file

<?xml version="1.0" encoding="UTF-8" ?>

<configuration>
    <appSettings>
        <remove key="some key" />
        <add key="some other key" value="some other value" />
    </appSettings>
</configuration>

The application that loads this application configuration file will no longer have the key-value pair with key “some key”, but it will have a key-value pair with key “some ...