My copy of Montemagnos FrenchPressTimer (for those times when I want a System.Timer in Xamarin.Forms PCL)

Timer.cs

using System;
using System.Threading;
using System.Threading.Tasks;

namespace ....Core.Control {
	// https://github.com/jamesmontemagno/FrenchPressTimer/blob/master/SimpleTimerPortable/Timer.cs
	internal delegate void TimerCallback(object state);

	internal sealed class Timer : CancellationTokenSource, IDisposable {
		public Timer(TimerCallback callback, object state, int dueTime, int period) {
			Task.Delay(dueTime, Token).ContinueWith(async (t, s) => {
				var tuple = (Tuple<TimerCallback, object>)s;

				while(true) {
					if(IsCancellationRequested)
						break;
					await Task.Run(() => tuple.Item1(tuple.Item2));
					await Task.Delay(period);
				}

			}, Tuple.Create(callback, state), CancellationToken.None,
				TaskContinuationOptions.ExecuteSynchronously | TaskContinuationOptions.OnlyOnRanToCompletion,
				TaskScheduler.Default);
		}

		public new void Dispose() { base.Cancel(); }
	}
}