ASP.NET中缓存非SQLServer数据库数据

在用非SqlServer数据库时，不能用.net自带的缓存类。那我们应该怎么做呢？

大致思路是：在application第一次启动的时候加载需要缓存的数据。然后每隔固定时间（比如1min）去更新缓存数据。

当需要查询的时候直接去查缓存中的时间，减少与DB交互。

具体看代码：

1.在Global中异步load所要缓存的数据：

首先定义一个全局的timer。

 Timer t = null;

2.在Application_Start中启动一个线程去load所需数据：

 protected void Application_Start()
 {
            //省略其他代码...

            Thread t = new Thread(Work);
            t.Start();
 }

 private void Work()
 {
            try
            {
                //log DateTime.Now
                System.Diagnostics.Stopwatch watcher = new System.Diagnostics.Stopwatch();
                watcher.Start();
                AdChina.Core.Helper.LogHelper.LogInfoFormat("start to load data from table:EA_CPS_REPORT_DATA... {0}", DateTime.Now);

                List<EaCpsReportData> reps = new DBHelper().GetInstance().Query<EaCpsReportData>("select * from EA_CPS_REPORT_DATA where status>-1").ToList<EaCpsReportData>();
                Dictionary<int, EaCpsReportData> dic = reps.ToDictionary(o => o.SerialId);
                HttpRuntime.Cache.Add("diccpsreportdata", dic, null, System.Web.Caching.Cache.NoAbsoluteExpiration, System.Web.Caching.Cache.NoSlidingExpiration, System.Web.Caching.CacheItemPriority.Default, null);

                watcher.Stop();
                long time = watcher.ElapsedMilliseconds;
                AdChina.Core.Helper.LogHelper.LogInfoFormat("after {0} ms,load data completed. {1}", time, DateTime.Now);
                TimerCallback callback = new TimerCallback(GetData);
                int dueTime = int.Parse(System.Configuration.ConfigurationManager.AppSettings["CacheDueTime"]);
                t = new Timer(callback, dueTime, 0, dueTime);
            }
            catch (Exception e)
            {
                //log here
            }
 }

private object lockobject = new object();

//从DB获取变更数据，根据key去更新Dictionary。
private void GetData(object o)
{
   try
   {      
      Dictionary<int, EaCpsReportData> dic = HttpRuntime.Cache["diccpsreportdata"] as Dictionary<int, EaCpsReportData>;
      if (dic == null) return;

      //1.查到1min所有变更数据
      int dueTime = (int)o * -2;
      List<EaCpsReportData> changed = new DBHelper().GetInstance().Query<EaCpsReportData>("select * from EA_CPS_REPORT_DATA where LAST_CHANGE >=  @0 order by LAST_CHANGE",
                                                                                                DateTime.Now.AddMilliseconds(dueTime)).ToList<EaCpsReportData>();

                lock (lockobject)
                {
                    //2.依次更新
                    foreach (var data in changed)
                    {
                        if (dic.ContainsKey(data.SerialId) && data.Status > 0)
                        {
                            dic[data.SerialId] = data;
                        }
                        else if (dic.ContainsKey(data.SerialId) && data.Status == -1)
                        {
                            dic.Remove(data.SerialId);
                        }
                        else if (!dic.ContainsKey(data.SerialId) && data.Status > 0)
                        {
                            dic.Add(data.SerialId, data);
                        }
                    }
                }

                HttpRuntime.Cache["diccpsreportdata"] = dic;
               
                if (changed.Count > 0) 
　　　　　　　　　 {
　　　　　　　　　　　　//log here
　　　　　　　　　 }

            }
            catch (Exception e)
            {
                //log here
            }
}

3.在查询的地方直接去查缓存里数据：

 Dictionary<int, EaCpsReportData> dic = System.Web.HttpRuntime.Cache["diccpsreportdata"] as Dictionary<int, EaCpsReportData>;

 if (dic == null)
 {
     // query from db
 }