using System;

using System.Runtime.CompilerServices;

​

public static class Program

{

​

    public static class DelegateKeeper

    {

        private static ConditionalWeakTable<object, object> cwtAction = new ConditionalWeakTable<object, object>();

        public static void KeepAlive(Action action) => cwtAction.Add(action.Target, new object());

    }

​

    public class SomeClass

    {

        public void DoSomething() { }

    }

​

    public static class GcHelper

    {

        public static void Collect()

        {

            // OK surely overkill but just to make sure. I will reduce it when everyting will be understood.

            GC.Collect(GC.MaxGeneration, GCCollectionMode.Forced, true);

            GC.WaitForPendingFinalizers();

​

            GC.Collect(GC.MaxGeneration, GCCollectionMode.Forced, true);

            GC.WaitForPendingFinalizers();

        }

    }

​

    static SomeClass inst;

    static WeakReference<Action> weakRef;

​

    public static void Main()

    {

        Proc1Scoped();

        GcHelper.Collect();

        Console.WriteLine($"weakRef.Target is alive = {weakRef.TryGetTarget(out _)}, expected true because inst keep a hold on SomeClass.");

​

        Proc2Scoped();

        GcHelper.Collect();

        Console.WriteLine($"weakRef.Target is alive = {weakRef.TryGetTarget(out _)}, expected false, because there is no more ref on SomeClass.");

    }

​

    private static void Proc1Scoped()

    {

        inst = new SomeClass();

        var action = inst.DoSomething;

        weakRef = new WeakReference<Action>(action);

        DelegateKeeper.KeepAlive(action);

    }

​

    private static void Proc2Scoped()

    {

        inst = null;

    }

}