public class XmlHelper
    {
        readonly string _xmlPath;
        public XmlHelper(string xmlPath)
        {
            _xmlPath = xmlPath;
        }

        /// <summary>
        /// 逐級讀取
        /// </summary>
        /// <returns></returns>
        public string ReadUrl()
        {
            XDocument xdoc = XDocument.Load(_xmlPath);
            string url = xdoc.Root.Element("url").Value;
            return url;
        }

        /// <summary>
        /// XPath讀取
        /// </summary>
        /// <returns></returns>
        public string ReadVersion()
        {
            XDocument xdoc = XDocument.Load(_xmlPath);
            string version = xdoc.XPathSelectElement("updateList/version").Value;
            return version;
        }

        /// <summary>
        /// Lambda讀取
        /// </summary>
        /// <returns></returns>
        public string FileNames()
        {
            XDocument xdoc = XDocument.Load(_xmlPath);
            string names = string.Join(",", xdoc.Root.Elements("files").Descendants("file").Select(s => s.Attribute("name").Value));
            return names;
        }

        /// <summary>
        /// linq讀取
        /// </summary>
        /// <returns></returns>
        public string FileVersions()
        {
            XDocument xdoc = XDocument.Load(_xmlPath);
            var versions = from elem in xdoc.Root.Elements("files").Descendants("file") select elem.Attribute("version").Value;
            return string.Join(",", versions);

        }

        /// <summary>
        /// 添加節(jié)點
        /// </summary>
        public void AddFile()
        {
            XDocument xdoc = XDocument.Load(_xmlPath);

            XElement addXele = new XElement("file");
            addXele.SetAttributeValue("name", "test.dll");
            addXele.SetAttributeValue("version", "2.00");

            xdoc.Root.Element("files").Add(addXele);
            xdoc.Save(_xmlPath);
        }

        /// <summary>
        /// 修改節(jié)點
        /// </summary>
        /// <param name="name"></param>
        /// <param name="version"></param>
        public void UpdateFile(string name, string version)
        {
            XDocument xdoc = XDocument.Load(_xmlPath);

            XElement xele = xdoc.Root.Elements("files").Descendants("file").FirstOrDefault(s => s.Attribute("name").Value == name);
            xele.SetAttributeValue("version", version);
            xdoc.Save(_xmlPath);
        }

        /// <summary>
        /// 刪除節(jié)點
        /// </summary>
        /// <param name="name"></param>
        public void DeleteFile(string name)
        {
            XDocument xdoc = XDocument.Load(_xmlPath);
            XElement xele = xdoc.Root.Elements("files").Descendants("file").FirstOrDefault(s => s.Attribute("name").Value == name);
            xele.Remove();
            xdoc.Save(_xmlPath);
        }
    }

string xmlPath = Application.StartupPath + "\\UpdateList.xml";

        private void btn_readxml_Click(object sender, EventArgs e)
        {
            text_xml.Text = File.ReadAllText(xmlPath);
        }

        private void btn_property_Click(object sender, EventArgs e)
        {
            XmlHelper xml = new XmlHelper(xmlPath);
            StringBuilder builder = new StringBuilder();
            builder.AppendLine("Url:" + xml.ReadUrl());
            builder.AppendLine("Version:" + xml.ReadVersion());
            builder.AppendLine("Names:" + xml.FileNames());
            builder.AppendLine("Versions:" + xml.FileVersions());

            text_property.Text = builder.ToString();
        }

        private void btn_add_Click(object sender, EventArgs e)
        {
            XmlHelper xml = new XmlHelper(xmlPath);
            xml.AddFile();
        }

        private void btn_update_Click(object sender, EventArgs e)
        {
            XmlHelper xml = new XmlHelper(xmlPath);
            xml.UpdateFile("test.dll", "3.00");
        }

        private void btn_delete_Click(object sender, EventArgs e)
        {
            XmlHelper xml = new XmlHelper(xmlPath);
            xml.DeleteFile("test.dll");
        }