static void DisplayAppSettings()
{
    try
    {
        var reader = new AppSettingsReader();

        NameValueCollection appSettings = ConfigurationManager.AppSettings;

        for (int i = 0; i < appSettings.Count; i++)
        {
            string key = appSettings.GetKey(i);
            string value = (string)reader.GetValue(key, typeof(string));
            Console.WriteLine("Key : {0} Value: {1}", key, value);
        }
    }
    catch (ConfigurationErrorsException e)
    {
        Console.WriteLine("[DisplayAppSettings: {0}]", e.ToString());
    }
}

//引入命名空间
using System;
using System.Configuration;

class MainClass
{
  static void Main(string[] args)
  {
    AppSettingsReader ar = new AppSettingsReader();
    Console.WriteLine("Here is your conn string");
    Console.WriteLine(ar.GetValue("appConStr", typeof(string)));
    Console.WriteLine();
    int numbOfTimes = (int)ar.GetValue("intValue", typeof(int));
    for(int i = 0; i < numbOfTimes; i++)
      Console.WriteLine("Yo!");
  }
}
/*
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appSettings>
    <add key="appConStr" value="server=localhost;uid=sa;pwd=;database=Cars" />
    <add key="intValue" value="4" />
  </appSettings>
</configuration>
*/