Android : Countdown timer in Android C#

I want to use countdown timer in my Android App using C#

this is the countdown timer class i am using

 public delegate void TickEvent(long millisUntilFinished);
public delegate void FinishEvent();

public class CountDown : CountDownTimer
{
    public event TickEvent Tick;
    public event FinishEvent Finish;

    Activity m_owner;
    public CountDown(long totaltime, long interval, Activity owner)
        : base(totaltime, interval)
    {
        m_owner = owner;           

    }

    public override void OnTick(long millisUntilFinished)
    {
        if (Tick != null)
            Tick(millisUntilFinished);
        long millis = millisUntilFinished;
        long hours = millis / (60 * 60 * 1000);
        long min = (millis / (60 * 1000)) % 60;
        long sec = (millis / 1000) % 60;
        TextView txtTime = m_owner.FindViewById<TextView>(Resource.Id.textTime);
        txtTime.Text = hours.ToString("00") + ":" + min.ToString("00") + ":" + sec.ToString("00");
    }

    public override void OnFinish()
    {
        if (Finish != null)
            Finish();
        var bulider = new AlertDialog.Builder(m_owner);
        bulider.SetMessage("Exam Time Over");
        bulider.SetCancelable(false);
        bulider.SetPositiveButton("OK", delegate { });
        var dialog1 = bulider.Create();
        dialog1.Show();

    }




}

now i want to call a function from "owner" Activity in timer onFinish(). Is there any way to do so?

Thanks.