让某一方法，在一定的周期内执行

using System.Timers;
using System.Windows.Threading;

      Timer cachingTimer = new Timer();//定义变量

       public void OnLoad(object sender, RoutedEventArgs e)
        {
            cachingTimer.Elapsed += new ElapsedEventHandler(onTimedEvent);
            cachingTimer.Interval = 50000;//50秒
            cachingTimer.Enabled = true;

         }

        private void onTimedEvent(object sender, ElapsedEventArgs e)//事件
        {
            Dispatcher.Invoke(DispatcherPriority.Normal, new updateUi(change_click));

        }

        private void change_click()//方法
        {
            NamespaceCaching.CachingE2LanguageType();//被周期调用的方法
        }