C# App.Config with array or list like data

The easiest way would be a comma separated list in your App.config file. Of course you can write your own configuration section, but what is the point of doing that if it is just an array of strings, keep it simple.

<configuration>
  <appSettings>
    <add key="ips" value="z,x,d,e" />
  </appSettings>
</configuration>

public string[] ipArray = ConfigurationManager.AppSettings["ips"].Split(',');