关于<appSettings file="app.config" >引用外部文件的配置值

<appSettings file="app.config">     
  </appSettings>

<?xml version="1.0" encoding="gb2312"?>
<appSettings>
  <!--平台名称-->
  <add key="PlatForm" value="嘻嘻嘻嘻嘻嘻嘻嘻嘻嘻嘻嘻嘻嘻嘻"/>
  <add key="DAL" value="MYTestDemo.SQLServerDAL"/>
  <add key="Skin" value="Red"/>
  <!--考试页面-->
  <add key="ExamUrl" value="Exam"/>

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

ConfigurationManager.OpenExeConfiguration

Configuration configs = ConfigurationManager.OpenExeConfiguration("aaa.config");

 //邮件设置
configs.AppSettings[MailConfigKey.FromAddr] = shopconfig.FromAddr;