Weak Event (c#)

[constructor-igor]

#33
https://www.codeproject.com/Articles/29922/Weak-Events-in-C
https://docs.microsoft.com/en-us/dotnet/framework/wpf/advanced/weak-event-patterns

[constructor-igor]

Show of problem with event.
We can see, GC doesn't show release publisher, when somebody (global subscriber) subscribed to event.

using System;

namespace WeakEventsDemo
{
    class Program
    {
        static void Main()
        {
            Console.WriteLine("[Main] started");

            Console.WriteLine("[Main] DemoPublisher_NoEvent");
            DemoPublisher_NoEvent();
            Console.WriteLine("[Main] DemoPublisher_Event_LocalSubscriber");
            DemoPublisher_Event_LocalSubscriber();
            Console.WriteLine("[Main] DemoPublisher_Event_GlobalSubscriber");
            DemoPublisher_Event_GlobalSubscriber();

            Console.WriteLine("[Main] Demo finished, Let's call GC");
            GC.Collect();
            GC.WaitForPendingFinalizers();
            Console.WriteLine("[Main] finished");
        }

        private static void DemoPublisher_NoEvent()
        {
            Publisher publisher = new Publisher();
            publisher.Run();
        }
        private static void DemoPublisher_Event_LocalSubscriber()
        {
            Subscriber subscriber = new Subscriber("local");
            Publisher publisher = new Publisher();
            publisher.MyEvent += subscriber.EventProcessing;
            publisher.Run();
        }
        private static readonly Subscriber m_globalSubscriber = new Subscriber("global");
        private static void DemoPublisher_Event_GlobalSubscriber()
        {
            Publisher publisher = new Publisher();
            publisher.MyEvent += m_globalSubscriber.EventProcessing;
            publisher.Run();
        }
    }
}

console

[global, 46104728] Subscriber.ctor()
[Main] started
[Main] DemoPublisher_NoEvent
[12289376] Publisher.ctor()
[12289376] Publisher.Run() started
[12289376] Publisher.Run() finished
[Main] DemoPublisher_Event_LocalSubscriber
[local, 43495525] Subscriber.ctor()
[55915408] Publisher.ctor()
[55915408] Publisher.Run() started
[local, 43495525] [event] args=System.EventArgs
[local, 43495525] [event] args=System.EventArgs
[55915408] Publisher.Run() finished
[Main] DemoPublisher_Event_GlobalSubscriber
[33476626] Publisher.ctor()
[33476626] Publisher.Run() started
[global, 46104728] [event] args=System.EventArgs
[global, 46104728] [event] args=System.EventArgs
[33476626] Publisher.Run() finished
[Main] Demo finished, Let's call GC
[33476626] Publisher.finalizer()
[12289376] Publisher.finalizer()
[55915408] Publisher.finalizer()
[local, 43495525] Subscriber.finalizer()
[Main] finished
[global, 46104728] Subscriber.finalizer()