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 first = new Account(1, 1000);
var second = new Account(2, 1000);
OwnedThreads.Run(() => { for (int i = 0; i < 100; i++) Transfer(first, second, 1); }, () => { for (int i = 0; i < 100; i++) Transfer(second, first, 1); });
Console.WriteLine($"a:{first.Balance}");
Console.WriteLine($"b:{second.Balance}");
Console.WriteLine($"total:{first.Balance + second.Balance}");
static void Transfer(Account from, Account to, int amount)
{
    if (amount < 1 || from.Id == to.Id) throw new ArgumentException("Distinct ordered accounts and positive amount required");
    Account low = from.Id < to.Id ? from : to, high = from.Id < to.Id ? to : from;
    lock (low.Sync) lock (high.Sync) { if (from.Balance < amount) throw new InvalidOperationException(); from.Balance -= amount; to.Balance += amount; }
}
sealed class Account(int id, int balance) { public int Id { get; } = id; public object Sync { get; } = new(); public int Balance = balance; }

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);
    }
}