System.Timers.Timer timer1 = new System.Timers.Timer();
timer1.Elapsed += new System.Timers.ElapsedEventHandler((obj, eventArg) => {
    Console.WriteLine("aaa");
});
timer1.Interval = 2000;//毫秒 1秒=1000毫秒
timer1.Enabled = true;//必须加上
timer1.AutoReset = false;//执行一次 false，一直执行true 
Console.ReadKey();