/// <summary>
        /// 修改XML
        /// </summary>
        /// <param>test</param>
        public static void ChangeXml(string str)
        {
            string xmlPath = "config";//当前文件夹下的config
            XmlDocument xmlDoc = new XmlDocument();
            xmlDoc.Load(xmlPath);
            XmlNodeList settings = xmlDoc.SelectNodes("con/app/user");
            foreach (XmlNode node in settings)
            {
                XmlNode valueNode = node.SelectSingleNode("value");
                string[] uri = valueNode.InnerText.Split(‘/‘);
                valueNode.InnerText = str;
            }
            xmlDoc.Save(configPath);
        }
原文:http://www.cnblogs.com/anyben/p/4364984.html