using System;

using System.Collections.Generic;

using System.Linq;

using System.Threading;

using System.Threading.Tasks;

public class Program

{

    private static SemaphoreSlim _sem = new(0, 1);

    private static async Task RunMeAsync()

    {

        Console.WriteLine("Before WaitAsync, tid = " + Thread.CurrentThread.ManagedThreadId);

        await _sem.WaitAsync();

        Console.WriteLine("After WaitAsync, tid = " + Thread.CurrentThread.ManagedThreadId); // Continue but on random thread.

        // ............. Dispatch to subscriber.

        await Task.Delay(2000);

        Console.WriteLine("Finish");

    }

​

    public static async Task Main()

    {

        var t1 = RunMeAsync(); // OnStart thread from DXF

        var t2 = RunMeAsync(); // Same DXF thread

        Console.WriteLine("====" + _sem.CurrentCount);

        _sem.Release(); // Event comes, let one go.

        _sem.Release(); // Event comes, let one go.

        Thread.Sleep(3000);

    }

}

​