WCF中静态变量要如何使用才安全？

Question

如 public static IList<DBIDConnStr> listDBIDConnStr = new List<DBIDConnStr>();

Answer 1

listDBIDConnStr这个是保存连接字符串的list，没有会加载一次，如果存在直接从这个对象中查询处理，使用basicHttpBinding，#region DB ConnStr
        /// <summary>
        /// connection string list
        /// </summary>
        public static IList<DBIDConnStr> listDBIDConnStr = new List<DBIDConnStr>();        /// <summary>
        /// load connection string
        /// </summary>
        private static void DefineConnStr(DBID dbID)
        {
            bool bConnSucceed = false;
            string connStrTmp = string.Empty;
            string path = AppDomain.CurrentDomain.BaseDirectory;
            if (!path.EndsWith("\\"))
                path += "\\";
            //read xml     
            XmlDocument xDoc = new XmlDocument();
            
            try
            {
                xDoc.Load(path + "Config.xml");
            }
            catch (Exception ex)
            {
                throw new Exception("xml读取失败" + ex.Message);
            }
            XmlNodeList listNodeXml = xDoc.SelectNodes("/Config/DB");
            foreach (XmlNode xn in listNodeXml)
            {
                string strType = "";
                try
                {
                    strType = xn.Attributes["Type"].Value;
                }
                catch { }
                if (xn.Attributes["Name"].Value.ToUpper().Equals(dbID.SubSystem.ToString().ToUpper())
                   && strType.ToUpper().Equals(dbID.Type.ToString().ToUpper()))
                {
                    string Server = xn.SelectSingleNode("/Config/DB/Server").InnerText;
                    string DB = xn.SelectSingleNode("/Config/DB/DataBase").InnerText;
                    string User = xn.SelectSingleNode("/Config/DB/User").InnerText;
                    string PWD = xn.SelectSingleNode("/Config/DB/PWD").InnerText;                    connStrTmp = string.Format(CONNECTIONSTRINGTEMPLETE, Server, DB,
                        User, commonFunc.MD5Decrypt(PWD));
                    try
                    {
                        commonFunc.GetSqlConnection(connStrTmp);
                        bConnSucceed = true;
                        break;
                    }
                    catch { }
                }
            }
            if (!bConnSucceed)
            {
                foreach (XmlNode xn in listNodeXml)
                {
                    string Server = xn.SelectSingleNode("/Config/DB/Server").InnerText;
                    string DB = xn.SelectSingleNode("/Config/DB/DataBase").InnerText;
                    string User = xn.SelectSingleNode("/Config/DB/User").InnerText;
                    string PWD = xn.SelectSingleNode("/Config/DB/PWD").InnerText;                    connStrTmp = string.Format(CONNECTIONSTRINGTEMPLETE, Server, DB,
                        User, commonFunc.MD5Decrypt(PWD));
                    try
                    {
                        commonFunc.GetSqlConnection(connStrTmp);
                        bConnSucceed = true;
                        break;
                    }
                    catch { }
                }
            }
            if (!bConnSucceed)
                throw new Exception("已有连接字符串无法正常连接服务器" + path);            //get db listconnstr
            string Sql = @"select b.Type,a.subSystemName,b.Model,b.Server,
                        b.[DataBase],b.[User],b.PWD from sys_SubSystem a with(nolock) 
                        left join sys_SubSystemDetail b with(nolock) 
                        on a.subSystemID=b.subSystemID order by b.Type";
            DataTable dt = commonFunc.GetDataTable(Sql, connStrTmp);            //init listdbidconnstr                
            foreach (DataRow dr in dt.Rows)
            {
                listDBIDConnStr.Add(new DBIDConnStr()
                {
                    Type = commonFunc.GetEnumByStringEx<DBIDType>(dr["Type"].ToString()),
                    SubSystem = dr["subSystemName"].ToString(),
                    Model = commonFunc.GetEnumByStringEx<DBIDModel>(dr["Model"].ToString()),
                    Server = dr["Server"].ToString(),
                    DataBase = dr["DataBase"].ToString(),
                    User = dr["User"].ToString(),
                    PWD = dr["PWD"].ToString()
                });
            }            //update xml
            xDoc.SelectSingleNode("/Config").RemoveAll();
            var vQuery = listDBIDConnStr.Where(p => p.Model == DBIDModel.Security);
            foreach (var vQry in vQuery)
            {
                XmlElement xe = xDoc.CreateElement("DB");
                xe.SetAttribute("Name", vQry.SubSystem.ToString());
                xe.SetAttribute("Type", vQry.Type.ToString());                XmlElement xc = xDoc.CreateElement("Server");
                xc.InnerText = vQry.Server;
                xe.AppendChild(xc);                xc = xDoc.CreateElement("DataBase");
                xc.InnerText = vQry.DataBase;
                xe.AppendChild(xc);                xc = xDoc.CreateElement("User");
                xc.InnerText = vQry.User;
                xe.AppendChild(xc);                xc = xDoc.CreateElement("PWD");
                xc.InnerText = vQry.PWD;
                xe.AppendChild(xc);                xDoc.SelectSingleNode("/Config").AppendChild(xe);
            }
            xDoc.Save(path + "Config.xml");
        }        /// <summary>
        /// Gets the conn STR.
        /// </summary>
        /// <param name="dbID">The db ID.</param>
        /// <returns></returns>
        /// <res></res>
        public static string getConnStr(DBID dbID)
        {
            //重新启动时读
            if (listDBIDConnStr.Count == 0)
            {
                DefineConnStr(dbID);
            }
            IList<DBIDConnStr> curDBIDConnstr = listDBIDConnStr.Where(p => p.Type == dbID.Type
                && p.SubSystem == dbID.SubSystem && p.Model == dbID.Model).ToList<DBIDConnStr>();
            //程序运行中，新增字符串重新读，不要重启程序
            if (curDBIDConnstr.Count() == 0)
            {
                DefineConnStr(dbID);
            }
            curDBIDConnstr = listDBIDConnStr.Where(p => p.Type == dbID.Type && p.SubSystem == dbID.SubSystem
                && p.Model == dbID.Model).ToList<DBIDConnStr>();
            if (curDBIDConnstr.Count() == 0)
            {
                throw new Exception(string.Format("连接字符串未定义 {0} {1} {2}", dbID.Type, dbID.SubSystem, dbID.Model));
            }
            string s=string.Format(CONNECTIONSTRINGTEMPLETE, curDBIDConnstr[0].Server,
                curDBIDConnstr[0].DataBase, curDBIDConnstr[0].User,
                commonFunc.MD5Decrypt(curDBIDConnstr[0].PWD));
            commonFunc.writeerrorlog("c:\\errorData2\\","",s);
            return s;
        }
        #endregion

Answer 2

如果只是初始化一边，后面不再变的话，可以使用Static Contractor:下面来自msdn: http://msdn.microsoft.com/en-us/library/aa645612.aspx
The static constructor for a class executes at most once in a given application domain. The execution of a static constructor is triggered by the first of the following events to occur within an application domain:An instance of the class is created.
Any of the static members of the class are referenced.更多讨论参考:
http://stackoverflow.com/questions/7095/is-the-c-sharp-static-constructor-thread-safe

Answer 3

非常感谢findcaiyzh,这个变量偶尔会有变化，

Answer 4

这篇文章讨论了list<t>的线程安全问题http://www.cnblogs.com/baihmpgy/archive/2011/07/13/2105018.html

Answer 5

.NET4.0里面有个BlockingCollection<T>类，可以替代List<T>,不过更倾向于使用ConcurrentDictionary<TKey,TValue>，那个可以通过唯一的“键”来达到同步目的，效果更佳。