读写XML文件问题

<?xml version="1.0"?>
<configuration>
  <appSettings>
    <add key="DBConStr" value="Data Source=wanglq;Initial Catalog=MKDB3;User ID=sa;Password=13948721800;Max Pool Size=300" />
    <add key="ClientSettingsProvider.ServiceUri" value="" />

    <add key="port" value="60100"/>
    <add key="vdir" value="/exam"/>
    <add key="page" value="default.aspx"/>
    <add key="path" value="exam"/>
  </appSettings>

  <system.runtime.remoting>
    <application>
      <client url="http://192.168.0.253:8100">
        <activated type="ActivateService, Service" />
      </client>
      <channels>
        <channel ref="http" port="0" />
      </channels>
    </application>
  </system.runtime.remoting> </configuration>

我写读写 <system.runtime.remoting>中的 <client url="http://192.168.0.253:8100">里的ur