Exception & thread safe event

gistfile1.cs

using System;
using System.Threading;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using NUnit.Framework;

namespace CustomEvent
{
    public sealed class Program
    {
        public event EventHandler CustomEvent
        {
            add
            {
                EventHandler current = _eventHandler, start;
                do
                {
                    start = current;
                    var desired = (EventHandler) Delegate.Combine(current, value);
                    current = Interlocked.CompareExchange(ref _eventHandler, desired, start);
                }
                while (start != current);
            }
            remove
            {
                EventHandler current = _eventHandler, start;
                do
                {
                    start = current;
                    var desired = (EventHandler) Delegate.Remove(current, value);
                    current = Interlocked.CompareExchange(ref _eventHandler, desired, start);
                }
                while (start != current);
            }
        }

        public /*protected*/ void RaiseCustomEvent(EventArgs e)
        {
            var handler = Volatile.Read(ref _eventHandler);
            if (handler == null)
            {
                return;
            }

            foreach (var h in handler.GetInvocationList().Cast<EventHandler>())
            {
                try
                {
                    h(this, e);
                }
                catch (Exception)
                {
                    // TODO: trace
                }
            }
        }

        private EventHandler _eventHandler;
    }

    [TestFixture]
    public class ProgramTest
    {
        [Test]
        public void Perform()
        {
            var p = new Program();
            const int NumberOfSubscribers = 10000;

            Task.WaitAll(Enumerable
                .Range(0, NumberOfSubscribers)
                .Select(_ => Task.Factory.StartNew(() =>
                {
                    p.CustomEvent += OnCustomEvent;
                }))
                .ToArray());

            p.RaiseCustomEvent(EventArgs.Empty);

            Assert.That(_counter, Is.EqualTo(NumberOfSubscribers));
            _counter = 0;

            Task.WaitAll(Enumerable
                .Range(0, NumberOfSubscribers)
                .Select(_ => Task.Factory.StartNew(() =>
                {
                    p.CustomEvent -= OnCustomEvent;
                }))
                .ToArray());

            p.RaiseCustomEvent(EventArgs.Empty);

            Assert.That(_counter, Is.EqualTo(0));
            _counter = 0;
        }

        private void OnCustomEvent(object o, EventArgs e)
        {
            Interlocked.Increment(ref _counter);
        }

        private int _counter;
    }
}