<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <connectionStrings>
    <add name="URL" connectionString="http://www.hao123.com"/>
    <add name="IP" connectionString="192.168.1.107"/>
  </connectionStrings>

  <appSettings>
    <add key="con" value="http://localhost/web"/>
  </appSettings>
</configuration>

 string conString = ConfigurationManager.AppSettings["con"];
 Console.WriteLine(conString);         
  string url = ConfigurationManager.ConnectionStrings["URL"].ConnectionString;
  Console.Write(url);