xml格式文件读取（读取网站自定义配置文件）

private static object obj = new object();
        private NameValueCollection _system = null;
        /// <summary>
        /// 得到系统配置表信息
        /// </summary>
        /// <returns>NameValueCollection 对象</returns>
        public  NameValueCollection GetSystem()
        {
            lock (obj)
            {
                if (_system == null)
                {
                    if (HttpContext.Current == null || HttpContext.Current.Cache == null || HttpContext.Current.Cache["system"] == null)
                    {
                        //read xml
                        string path = AppDomain.CurrentDomain.BaseDirectory + "config\\data.config";
                        initSystemConfig();
                        NameValueCollection nvc = new NameValueCollection();
                        XmlDocument Doc_Detail = new XmlDocument();
                        Doc_Detail.Load((path));
                        XmlNodeList NodeList = Doc_Detail.SelectNodes("/root/system/*");
                        if (NodeList.Count > 0)
                        {
                            for (int i = 0; i < NodeList.Count; i++)
                            {

                                if (NodeList[i] != null)
                                {
                                    nvc.Add(NodeList[i].Name, NodeList[i].InnerText);
                                }

                            }
                        }
                        _system = nvc;
                        if (HttpContext.Current != null)
                            HttpContext.Current.Cache.Add("system", nvc, new System.Web.Caching.CacheDependency(HttpContext.Current.Server.MapPath("/config/data.config")), System.Web.Caching.Cache.NoAbsoluteExpiration, System.Web.Caching.Cache.NoSlidingExpiration, System.Web.Caching.CacheItemPriority.Default, null);
                    }
                    else
                    {
                        _system = (NameValueCollection)HttpContext.Current.Cache["system"];

                    }
                }
            }
            return _system;
        }
 /// <summary>
        /// 初始化文件信息
        /// </summary>
        private void initSystemConfig()
        {
            string path1 = AppDomain.CurrentDomain.BaseDirectory+"config";
            if (!Directory.Exists(path1))
            {
                Directory.CreateDirectory(path1);

            }
            string path = AppDomain.CurrentDomain.BaseDirectory+"config\\data.config";
            FileInfo CreateFile = new FileInfo(path); //创建文件
            if (!CreateFile.Exists)
            {
                FileStream FS = CreateFile.Create();
                FS.Close();

                StreamWriter SW;
                SW = File.AppendText(path);
                SW.WriteLine("<?xml version=\"1.0\"?><root><system></system></root>");
                SW.Close(); 
            }
        }

//知识点：
//NameValueCollection  作为键值对存储数据
//xmlDoc.SelectNodes("/root/system/*"); 以反斜杠"/"分开得到可以 XmlNodeList 列表。