C# android timer dont work

I try to make timer in android app.

This is code.

Doesn't work

public class Activity1 : Activity

{

int count = 1;

TextView txv1;

System.Timers.Timer t1;

protected override void OnCreate(Bundle bundle)

{

base.OnCreate(bundle);

// Set our view from the "main" layout resource

SetContentView(Resource.Layout.Main);

// Get our button from the layout resource,

// and attach an event to it

// Button button = FindViewById

txv1 = FindViewById(Resource.Id.textView7);

DateTime dt = DateTime.Now;

//txv1.Text = dt.ToShortTimeString();

txv1.Text = dt.ToLongTimeString();

t1 = new System.Timers.Timer(100);

t1.Elapsed += new ElapsedEventHandler(OnTimeEvent);

//t1.Interval = 100;

t1.Enabled = true;

t1.Start();

}

private void OnTimeEvent(object source, ElapsedEventArgs e)

{

txv1.Text = count.ToString();

count++;

}

I need help.

Thanks