private void button1_Click(object sender, EventArgs e)
        {
            MusteriKayit Mk = new MusteriKayit();

            this.Hide();
            Mk.Show();
        }
        private void button3_Click(object sender, EventArgs e)
        {
            MusteriKayit m = new MusteriKayit();

            this.Hide();
            m.Show();
            m.tabControl1.SelectTab(1);
        }