private volatile bool lezarva = false, leallit = false;
private ConcurrentQueue<string> sor = new ConcurrentQueue<string>();
private Stopwatch meroOra = Stopwatch.StartNew();
private long utolsoTick = 0, legnagyobb = 0;
private int futo = 0;

private void Form1_Load(object sender, EventArgs e)
{
    tmrMero.Interval = 50; tmrMero.Start();
    tmrNaplo.Interval = 100;
}

private void tmrMero_Tick(object sender, EventArgs e)
{
    long most = meroOra.ElapsedMilliseconds;
    long keses = most - utolsoTick - tmrMero.Interval;

    utolsoTick = most;
    if (keses > legnagyobb) { legnagyobb = keses; }
    lblKeses.Text = "Legnagyobb késés: " + legnagyobb + " ms";
}

private void Form1_FormClosing(object sender, FormClosingEventArgs e) { lezarva = true; leallit = true; tmrNaplo.Stop(); tmrMero.Stop(); }

private void BiztonsagosFrissit(Action muvelet)
{
    if (lezarva || IsDisposed || !IsHandleCreated) { return; }

    try { BeginInvoke(muvelet); }
    catch (ObjectDisposedException) { }
    catch (InvalidOperationException) { }
}

private async void btnIndit_Click(object sender, EventArgs e)
{
    int db = (int)nudDb.Value, mod = cmbMod.SelectedIndex;

    lstNaplo.Items.Clear();
    legnagyobb = 0;
    leallit = false;
    sor = new ConcurrentQueue<string>();
    btnIndit.Enabled = false;

    Progress<string> halad = new Progress<string>(s => lstNaplo.Items.Add(s));   // a felületi szálon létrehozva
    Stopwatch sw = Stopwatch.StartNew();
    long termeles = 0;

    try
    {
        if (mod == 2) { tmrNaplo.Start(); }

        await Task.Run(() =>
        {
            for (int i = 0; i < db && !leallit; i++)
            {
                string s = "sor " + i;

                if (mod == 0) { BiztonsagosFrissit(() => lstNaplo.Items.Add(s)); }
                else if (mod == 1) { ((IProgress<string>)halad).Report(s); }
                else { sor.Enqueue(s); }
            }
        });

        termeles = sw.ElapsedMilliseconds;

        // várjuk meg, amíg a felület feldolgozza az utolsó sort is
        if (mod == 2) { while (!sor.IsEmpty && !lezarva) { await Task.Delay(50); } }
        else { await Task.Delay(50); }

        if (lezarva) { return; }

        lstEredmeny.Items.Insert(0, cmbMod.Text + ": termelés " + termeles + " ms, kiürülés " + sw.ElapsedMilliseconds + " ms, legnagyobb késés " + legnagyobb + " ms");
    }
    finally
    {
        tmrNaplo.Stop();

        if (!IsDisposed) { btnIndit.Enabled = true; }
    }
}

private void tmrNaplo_Tick(object sender, EventArgs e)
{
    List<string> adag = new List<string>();
    string s;

    while (adag.Count < 500 && sor.TryDequeue(out s)) { adag.Add(s); }

    if (adag.Count == 0) { return; }

    lstNaplo.BeginUpdate();
    lstNaplo.Items.AddRange(adag.ToArray());

    while (lstNaplo.Items.Count > 2000) { lstNaplo.Items.RemoveAt(0); }

    lstNaplo.EndUpdate();
    lstNaplo.TopIndex = lstNaplo.Items.Count - 1;
}

private void btnMegse_Click(object sender, EventArgs e) { leallit = true; }

// ---- versenyhelyzet ----
private async void btnVerseny_Click(object sender, EventArgs e)
{
    btnVerseny.Enabled = false;

    try
    {
        long sima = 0, atomi = 0, zart = 0;
        object zar = new object();
        Stopwatch sw = Stopwatch.StartNew();

        await Task.WhenAll(Enumerable.Range(0, 4).Select(k => Task.Run(() => { for (int i = 0; i < 1000000; i++) { sima++; } })));
        long t1 = sw.ElapsedMilliseconds; sw.Restart();
        await Task.WhenAll(Enumerable.Range(0, 4).Select(k => Task.Run(() => { for (int i = 0; i < 1000000; i++) { Interlocked.Increment(ref atomi); } })));
        long t2 = sw.ElapsedMilliseconds; sw.Restart();
        await Task.WhenAll(Enumerable.Range(0, 4).Select(k => Task.Run(() => { for (int i = 0; i < 1000000; i++) { lock (zar) { zart++; } } })));
        long t3 = sw.ElapsedMilliseconds;

        lstEredmeny.Items.Insert(0, "Várt: 4 000 000 | sima ++: " + sima + " (" + t1 + " ms) | Interlocked: " + atomi + " (" + t2 + " ms) | lock: " + zart + " (" + t3 + " ms)");
    }
    finally { if (!IsDisposed) { btnVerseny.Enabled = true; } }
}