ASP.NET读取XML的问题(C#+JAVASCRIPT)
XML格式如下:

<?xml   version= "1.0 "   encoding= "utf-8 "?>
<MsgList>

    <Class   name= "全局消息 ">
        <Item   name= "返回结果成功 "   code= "100 "   const= "RESULT_OK "     msg= "返回结果成功! "/>
        <Item   name= "提交时ILK值错误 "   code= "100 "   const= "RESULT_ILK_ERROR "     msg= "找不到该模块! "/>
        <Item   name= "提交时参数错误 "   code= "102 "   const= "RESULT_PARM_ERROR "     msg= "参数错误! "/>
    </Class>
    <Class   name= "管理员消息 ">
        <Item   name= "登录成功 "   code= "100 "   const= "RESULT_ADMIN_LOGIN_OK "     msg= "登录成功! "/>
        <Item   name= "登录验证码错误 "   code= "102 "   const= "RESULT_ADMIN_VERIFY_ERROR "     msg= "验证码错误! "/>
        <Item   name= "登录帐号或密码错误 "   code= "103 "   const= "RESULT_ADMIN_PWD_ERROR "     msg= "帐号或密码错误! "/>
        <Item   name= "登录帐号被冻结 "   code= "104 "   const= "RESULT_ADMIN_FREEZE "     msg= "此帐号已被冻结! "/>
        <Item   name= "登录帐号被冻结 "   code= "204 "   const= "RESULT_ADMINGROUP_FREEZE "     msg= "此帐号已被冻结! "/>
    </Class>
    <Class   name= "留言本消息 ">
        <Item   name= "留言成功 "   code= "800 "   const= "RESULT_GBOOK_MSG_OK "     msg= "留言成功!谢谢您的留言! "/>
        <Item   name= "留言数据库错误 "   code= "801 "   const= "RESULT_GBOOK_MSG_DATABASE_ERROR "     msg= "留言失败!请重试! "/>
        <Item   name= "名称为空 "   code= "803 "   const= "RESULT_GBOOK_NAME_EMPTY "     msg= "请问大虾贵姓?! "/>
        <Item   name= "名称越界 "   code= "804 "   const= "RESULT_GBOOK_NAME_BOUND "     msg= "称呼过长,限制为6个中文汉字! "/>
        <Item   name= "联系方式为空 "   code= "805 "   const= "RESULT_GBOOK_CONTACT_EMPTY "     msg= "请输入联系方式! "/>
        <Item   name= "联系方式越界 "   code= "806 "   const= "RESULT_GBOOK_CONTACT_BOUND "     msg= "联系方式不能超过40个中文汉字! "/>
        <Item   name= "留言内容为空 "   code= "807 "   const= "RESULT_GBOOK_TEXT_EMPTY "     msg= "请输入留言内容! "/>
        <Item   name= "留言内容越界 "   code= "808 "   const= "RESULT_GBOOK_TEXT_BOUND "     msg= "留言内容不能超过100个中文汉字! "/>
    </Class>

</MsgList>

要求:
C#中传入宏名(const的值)取得代码(code的值),然后返回这个值到客户端,客户端通过这个值取得消息(