// 定时器
        static Timer statsTimer;
        static Timer emailTimer;

        // 定时间隔
        private long EmailInterval = ForumConfiguration.GetConfig().ThreadIntervalEmail * 60000;
        private long StatsInterval = ForumConfiguration.GetConfig().ThreadIntervalStats * 60000;

        public String ModuleName { 
            get { return "ForumsHttpModule"; } 
        }    


        // *********************************************************************
        //  ForumsHttpModule
        //
        /**//// <summary>
        /// Initializes the HttpModule and performs the wireup of all application
        /// events.
        /// </summary>
        /// <param name="application">Application the module is being run for</param>
        public void Init(HttpApplication application) { 

            // Wire-up application events
            //
            // 略去其他代码
            
            ForumConfiguration forumConfig = ForumConfiguration.GetConfig();

            // 如果使用定时器并且定时器还没初始化
            if( forumConfig != null
            &&  forumConfig.IsBackgroundThreadingDisabled == false ) {
                if (emailTimer == null)
                    // 新建定时器
                    // 新建一个TimerCallback委托，具体要执行的方法在ScheduledWorkCallbackEmailInterval中
                    emailTimer = new Timer(new TimerCallback(ScheduledWorkCallbackEmailInterval), application.Context, EmailInterval, EmailInterval);

                if( forumConfig.IsIndexingDisabled == false 
                &&    statsTimer == null ) {
                    statsTimer = new Timer(new TimerCallback(ScheduledWorkCallbackStatsInterval), application.Context, StatsInterval, StatsInterval);
            }
        }
        }

        /**//// <summary>
        /// 释放定时器
        /// </summary>
        public void Dispose() {
            statsTimer = null;
            emailTimer = null;
        }

        Timer Callbacks#region Timer Callbacks
        /**//// <summary>
        /// 定时发送队列中待发送的邮件
        /// </summary>
        private void ScheduledWorkCallbackEmailInterval (object sender) {
            try {
                // 当处理邮件时暂停定时器
                emailTimer.Change( System.Threading.Timeout.Infinite, EmailInterval );

                // 发送队列中的邮件
                //
                Emails.SendQueuedEmails( (HttpContext) sender);


                // 更新匿名用户
                //
                Users.UpdateAnonymousUsers( (HttpContext) sender);
            }
            catch( Exception e ) {
                ForumException fe = new ForumException( ForumExceptionType.EmailUnableToSend, "Scheduled Worker Thread failed.", e );
                fe.Log();
            }
            finally {
                // 重新启动定时器
                emailTimer.Change( EmailInterval, EmailInterval );
            }
        }

        /**//// <summary>
        /// 定时索引帖子和定时更新论坛统计信息
        /// </summary>
        private void ScheduledWorkCallbackStatsInterval(object sender) {
            try {
                // 休眠定时器
                statsTimer.Change( System.Threading.Timeout.Infinite, StatsInterval );

                // 每次索引100篇帖子
                //
                Search.IndexPosts( (HttpContext) sender, 100);

                // 更新论坛统计信息
                SiteStatistics.LoadSiteStatistics( (HttpContext) sender, true, 1 );
            }
            catch( Exception e ) {
                ForumException fe = new ForumException( ForumExceptionType.UnknownError, "Failure performing scheduled statistics maintenance.", e );
                fe.Log();
            }
            finally {
                // 唤醒定时器
                statsTimer.Change( StatsInterval, StatsInterval);
            }
        }
        #endregion