private void button1_Click(object sender, EventArgs e)
{
    double sayi1, sayi2, sayi3, sayi4;

    sayi1 = Convert.ToDouble(textBox4.Text);
    sayi2 = Convert.ToDouble(textBox5.Text);
    sayi3 = Convert.ToDouble(textBox6.Text);
    sayi4 = Convert.ToDouble(textBox7.Text);
    double maxSayi = Math.Max(sayi1, Math.Max(sayi2, Math.Max(sayi3, sayi4)));
    double[] sayilar = { sayi4, sayi3, sayi2, sayi1 };
    MessageBox.Show($"sıralama: {string.Join(" ", sayilar)}");
}