private void btnprev_Click(object sender, EventArgs e)
        {
            AnaEkran geri = new AnaEkran();

            this.Hide();
            geri.Show();
        }
        private void anaEkranaDönToolStripMenuItem_Click(object sender, EventArgs e)
        {
            AnaEkran geri = new AnaEkran();

            this.Hide();
            geri.Show();
        }