using System;
using System.Collections.Generic;
using System.Text;
using System.Reflection;

namespace CheckEventSubscription
{
    class Program
    {
        public static bool IsSubscribed(object eventPublisher, string eventName, object possibleSubscriber)
        {
            // Get the fieldinfo for the internal delegate.
            FieldInfo delegateField = eventPublisher.GetType().GetField(eventName, BindingFlags.NonPublic | BindingFlags.Instance);

            // Get the actual delegate instance.
            Delegate del = delegateField.GetValue(eventPublisher) as Delegate;

            bool isSubscribed = false;

            // Remember - if no-one's subscribed, the delegate is null (therefore, return false).
            if (del != null)
            {
                // Go over all the members on the Multicast delegate.
                foreach (Delegate handler in del.GetInvocationList())
                {
                    if (handler.Target == possibleSubscriber)
                        isSubscribed = true;
                }
            }

            return isSubscribed;

        }

        static void Main(string[] args)
        {

            EventPublisher ep = new EventPublisher();
            EventSubscriber es = new EventSubscriber();

            bool isSubscribed = false;

            ep.Event += es.EventHandler;
            isSubscribed = IsSubscribed(ep, "Event", es);

            ep.Event -= es.EventHandler;
            isSubscribed = IsSubscribed(ep, "Event", es);
        }

    }

    public class EventSubscriber
    {
        public void EventHandler(object sender, EventArgs e)
        {
        }
    }

    public class EventPublisher
    {
        public event EventHandler<EventArgs> Event;

    }
}