如何从diff应用程序中读取app.config中的用户设置？

// 在app.config中定义userSettings sectionGroup和userSettings section<configuration>
 <configSections>
   <sectionGroup name="userSettings">
     <section name="userSettings" type="System.Configuration.NameValueSectionHandler" />
    </sectionGroup>
  </configSections>

  // 在userSettings section中定义userName key
  <userSettings>
    <userSettings>
      <add key="userName" value="John Doe" />
    </userSettings>
  </userSettings>
</configuration>

// 在应用程序代码中读取userName key的值
string userName = ConfigurationManager.GetSection("userSettings/userSettings")["userName"] as string;