C# broadcast signaled event via Task completion

BroadcastEventSample.cs

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

namespace BroadcastEventSample
{
    public class EventBroadcastTask
    {
        private readonly CancellationTokenSource cancelSource = new CancellationTokenSource();
        private readonly TaskCompletionSource<bool> tcs = new TaskCompletionSource<bool>();

        public EventBroadcastTask()
        {
            cancelSource.Token.Register(WhenCanceled, tcs);
        }

        public Task CompletionTask => tcs.Task;
        public bool Signaled { get; private set; }

        public void Signal()
        {
            if (!Signaled)
            {
                Signaled = true;
                cancelSource.Cancel();
            }
        }

        private void WhenCanceled(object s)
        {
            ((TaskCompletionSource<bool>)s).SetResult(true);
        }
    }

    class Program
    {
        static void Main(string[] args)
        {

            var someEvent = new EventBroadcastTask();

            Console.WriteLine("Press ENTER to complete all tasks");

            var tasks = new[]
            {
                Task.Run( async () => { await someEvent.CompletionTask; Console.WriteLine("task 1 complete"); } ),
                Task.Run( async () => { await someEvent.CompletionTask; Console.WriteLine("task 2 complete"); } ),
                Task.Run( () => { Console.ReadLine(); someEvent.Signal(); })
            };

            Task.WaitAll(tasks);

            Console.WriteLine("all done");
        }
    }
}