<?xml version="1.0" encoding="utf-8" ?>
<configuration>
 <appSettings>
 <add key="theDate" value="2015-07-20 16:25"/>
 <add key="theName" value="Alice"/>
 <add key="theType" value="NBA"/>
 <add key="thePrice" value="12500.00"/>
 </appSettings>
</configuration>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Configuration;

namespace AppConfigDemo
{
 class Program
 {
  static void Main(string[] args)
  {
   //判断App.config配置文件中是否有Key(非null)
   if (ConfigurationManager.AppSettings.HasKeys())
   {
    //循环遍历出配置文件中的所有的键Key
    foreach (string s in ConfigurationManager.AppSettings)
    {
     Console.WriteLine(s);
    }
   }
   Console.ReadKey();
  }
 }
}

 static void Main(string[] args)
  {
   //判断App.config配置文件中是否有Key(非null)
   if (ConfigurationManager.AppSettings.HasKeys())
   {
    //循环遍历出配置文件中的所有的键Key
    for (int i = 0; i < ConfigurationManager.AppSettings.Count; i++)
    {
     Console.WriteLine(ConfigurationManager.AppSettings.GetKey(i));
    }
   }
   Console.ReadKey();
  }

static void Main(string[] args)
  {
   //判断App.config配置文件中是否有Key(非null)
   if (ConfigurationManager.AppSettings.HasKeys())
   {
    //获取“theDate”键的Value
    foreach (string s in ConfigurationManager.AppSettings.GetValues("theDate"))
    {
     Console.WriteLine(s);
    }
   }
   Console.ReadKey();
  }

 static void Main(string[] args)
  {
   //判断App.config配置文件中是否有Key(非null)
   if (ConfigurationManager.AppSettings.HasKeys())
   {
    List<string> theKeys = new List<string>(); //保存Key的集合
    List<string> theValues = new List<string>(); //保存Value的集合
    //遍历出所有的Key并添加进theKeys集合
    foreach (string theKey in ConfigurationManager.AppSettings.Keys)
    {
     theKeys.Add(theKey);
    }
    //根据Key遍历出所有的Value并添加进theValues集合
    for (int i = 0; i < theKeys.Count; i++)
    {
     foreach (string theValue in ConfigurationManager.AppSettings.GetValues(theKeys[i]))
     {
      theValues.Add(theValue);
     }
    }
    //验证一下
    Console.WriteLine("*************Key*************");
    foreach (string s in theKeys)
    {
     Console.WriteLine(s);
    }
    Console.WriteLine("************Value************");
    foreach (var item in theValues)
    {
     Console.WriteLine(item);
    }
   }
   Console.ReadKey();
  }