Configuration system failed to initialize

Problem:
  Visual Studio 2010
  .NET Framework 4


  System.Configuration.ConfigurationManager.AppSettings["IP"]

  Error = Configuration system failed to initialize


Solution:


  Move <appSettings> to the first node.

  <configuration>

<appSettings>
<add key="IP" value="192.xxx.xxx.xx" />
<add key="Port" value="xxxx" />
</appSettings>

<startup>
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/>
</startup>

<connectionStrings>
<add name="db" connectionString="..."
providerName="Oracle.DataAccess.Client" />
</connectionStrings>

  </configuration>