OpenNETCF.WindowsCE.LargeIntervalTimer llTimer = new OpenNETCF.WindowsCE.LargeIntervalTimer(); 

//第一次触发时间

llTimer.FirstEventTime = DateTime.Now;

llTimer.Interval = new TimeSpan(0, 30, 0);

//是否只触发一次

 llTimer.OneShot = false;

llTimer.Tick += new EventHandler(llTimer_Tick);

llTimer.Enabled = true;

static void llTimer_Tick(object sender, EventArgs e)

 {

             //

  }

 

来源：http://www.cnblogs.com/fox23/archive/2008/02/03/AtTime.html

opennetcf下载：http://www.opennetcf.com/Products/SmartDeviceFramework/tabid/65/Default.aspx