private void Form1_Load(object sender, EventArgs e)
{
    string[] jelek = { "7", "8", "9", "÷", "4", "5", "6", "×", "1", "2", "3", "-", "0", ",", "=", "+" };

    tlpGombok.ColumnCount = 4;
    tlpGombok.RowCount = 4;
    tlpGombok.ColumnStyles.Clear();
    tlpGombok.RowStyles.Clear();

    for (int i = 0; i < 4; i++)
    {
        tlpGombok.ColumnStyles.Add(new ColumnStyle(SizeType.Percent, 25));
        tlpGombok.RowStyles.Add(new RowStyle(SizeType.Percent, 25));
    }

    for (int i = 0; i < jelek.Length; i++)
    {
        Button gomb = new Button();
        gomb.Text = jelek[i];
        gomb.Dock = DockStyle.Fill;
        gomb.Tag = jelek[i];
        gomb.Click += Gomb_Click;

        tlpGombok.Controls.Add(gomb, i % 4, i / 4);   // oszlop: maradék, sor: egész osztás
    }
}

private void Gomb_Click(object sender, EventArgs e)
{
    txtKijelzo.Text = txtKijelzo.Text + ((Button)sender).Tag;
}

private void Form1_Load(object sender, EventArgs e)
{
    Random r = new Random();

    for (int i = 0; i < 12; i++)
    {
        Panel negyzet = new Panel();
        negyzet.BackColor = Color.FromArgb(r.Next(60, 230), r.Next(60, 230), r.Next(60, 230));
        negyzet.Size = new Size(trbMeret.Value, trbMeret.Value);
        flpGaleria.Controls.Add(negyzet);
    }
}

private void trbMeret_Scroll(object sender, EventArgs e)
{
    flpGaleria.SuspendLayout();

    foreach (Control c in flpGaleria.Controls)
    {
        c.Size = new Size(trbMeret.Value, trbMeret.Value);
    }

    flpGaleria.ResumeLayout();
}

private void btnUjSor_Click(object sender, EventArgs e)
{
    Panel sor = new Panel();
    sor.Size = new Size(flpSorok.ClientSize.Width - 25, 32);

    TextBox termek = new TextBox { Location = new Point(0, 4), Width = 200 };
    NumericUpDown db = new NumericUpDown { Location = new Point(210, 4), Width = 70, Minimum = 1, Value = 1 };
    Button torol = new Button { Text = "Törlés", Location = new Point(290, 2), Tag = sor };

    torol.Click += SorTorol_Click;

    sor.Controls.Add(termek);
    sor.Controls.Add(db);
    sor.Controls.Add(torol);
    flpSorok.Controls.Add(sor);
}

private void SorTorol_Click(object sender, EventArgs e)
{
    Button torol = (Button)sender;
    Panel sor = (Panel)torol.Tag;

    torol.Click -= SorTorol_Click;
    flpSorok.Controls.Remove(sor);
    sor.Dispose();   // a gyermekeit is felszabadítja
}

Button mentes = new Button();
mentes.Text = "Mentés";
mentes.Dock = DockStyle.Fill;

tlp.Controls.Add(mentes, 1, 3);

Label cim = new Label();
cim.Text = "Új felhasználó";
cim.Dock = DockStyle.Fill;
cim.TextAlign = ContentAlignment.MiddleCenter;
cim.Font = new Font(cim.Font.FontFamily, 14, FontStyle.Bold);

tlp.Controls.Add(cim, 0, 0);
tlp.SetColumnSpan(cim, 2);

Label gyumolcs = new Label { Text = "Gyümölcsök", AutoSize = true, Font = new Font(Font, FontStyle.Bold) };
flp.Controls.Add(gyumolcs);
flp.SetFlowBreak(gyumolcs, true);   // a cím után új sor

foreach (string nev in new string[] { "Alma", "Körte", "Szilva" })
{
    flp.Controls.Add(new Button { Text = nev, AutoSize = true });
}

private long Meres(bool felfuggeszt)
{
    System.Diagnostics.Stopwatch ora = System.Diagnostics.Stopwatch.StartNew();

    flp.Controls.Clear();

    if (felfuggeszt)
    {
        flp.SuspendLayout();
    }

    for (int i = 0; i < 300; i++)
    {
        flp.Controls.Add(new Button { Text = i.ToString(), Width = 50 });
    }

    if (felfuggeszt)
    {
        flp.ResumeLayout();
    }

    ora.Stop();
    return ora.ElapsedMilliseconds;
}

private void btnMeres_Click(object sender, EventArgs e)
{
    long nelkul = Meres(false);
    long vele = Meres(true);

    lblEredmeny.Text = $"Nélküle: {nelkul} ms, vele: {vele} ms";
}