asp.net操作XML

using System;
using System.Xml;

public partial class Web_Admin_Admin_Basic : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            string sFile = Server.MapPath("../Web.config");
            XmlDocument xmldoc = new XmlDocument();
            xmldoc.Load(sFile);

            XmlNodeList topm = xmldoc.DocumentElement.ChildNodes;
            foreach (XmlElement element in topm)
            {
                if (element.Name.ToLower() == "appsettings")
                {
                    XmlNodeList _node = element.ChildNodes;
                    if (_node.Count > 0)
                    {
                        foreach (XmlElement el in _node)
                        {
                            if (el.Attributes["key"].InnerXml == "IsOpenWin")
                                RadioButtonList1.SelectedValue = el.Attributes["value"].Value;
                        }
                    }
                }
            }
        }
    }

    protected void Button1_Click(object sender, EventArgs e)
    {
        string sFile = Server.MapPath("../Web.config");
        XmlDocument xmldoc = new XmlDocument();
        xmldoc.Load(sFile);

        XmlNodeList topm = xmldoc.DocumentElement.ChildNodes;
        foreach (XmlElement element in topm)
        {
            if (element.Name.ToLower() == "appsettings")
            {
                XmlNodeList _node = element.ChildNodes;
                if (_node.Count > 0)
                {
                    foreach (XmlElement el in _node)
                    {
                        if (el.Attributes["key"].InnerXml == "IsOpenWin")
                            el.Attributes["value"].Value = RadioButtonList1.SelectedValue;
                    }
                }
            }
        }
        xmldoc.Save(sFile);
        Common.Message("<script>alert('修改成功');location.href='Admin_Basic.aspx'</script>");
    }
}