public override void ViewDidLoad() { base.ViewDidLoad(); // Perform any additional setup after loading the view, typically from a nib. btnStart.Enabled = true; btnStop.Enabled = false; //btnReset.Enabled = true; btnStart.TouchUpInside += delegate { btnStart.Enabled = false; btnStop.Enabled = true; timer = NSTimer.CreateRepeatingScheduledTimer(TimeSpan.FromSeconds(1), timer_tick); }; btnStop.TouchUpInside += delegate { btnStart.Enabled = true; btnStop.Enabled = false; timer.Invalidate(); }; btnReset.TouchUpInside += delegate { MyTimerLogic.Rest(); lblDisplay.Text = MyTimerLogic.GetCurrentTickCount(); btnStart.Enabled = true; btnStop.Enabled = false; }; }