有这样一个xml
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appsettings>
  <Bassettings>
   <settingname="A" ser="String">
    <value>0<value>
      </setting>
   <settingname="B" ser="String">
    <value>10000<value>
      </setting>

   </Bassettings>
</appsettings>
</configuration>

如何获取A的value，和B的value，并且修改保存 麻烦大神解决下