using System;
using System.Linq;
using System.Collections.Generic;
using System.Collections.Concurrent;
using System.Reflection;
using System.Linq.Expressions;
using System.Threading;
using System.Threading.Tasks;

var sync = new object();
bool rejected = false;
lock (sync)
{
    lock (sync) { if (!Monitor.IsEntered(sync)) throw new InvalidOperationException(); }
    OwnedThreads.Run(() => { try { Monitor.Exit(sync); } catch (SynchronizationLockException) { rejected = true; } });
}
Console.WriteLine($"wrong-owner:{rejected}");
Console.WriteLine($"after:{Monitor.IsEntered(sync)}");

public static class OwnedThreads
{
    public static void Run(params Action[] actions)
    {
        var errors = new ConcurrentQueue<Exception>();
        var threads = actions.Select(action => new Thread(() => { try { action(); } catch (Exception error) { errors.Enqueue(error); } }) { IsBackground = true }).ToArray();
        foreach (var thread in threads) thread.Start();
        foreach (var thread in threads) if (!thread.Join(TimeSpan.FromSeconds(8))) throw new TimeoutException("Owned worker did not finish");
        if (!errors.IsEmpty) throw new AggregateException(errors);
    }
}