private void btnDuzenle_Click(object sender, EventArgs e)
        {
            m.Username  = txtMail.Text;
            m.Password  = txtSifre.Text;
            m.Firstname = txtAdi.Text;
            m.Lastname  = txtSoyadi.Text;
            m.Mail      = txtMail.Text;
            m.Phone     = txtTelefon.Text;
            string cevap = BLLMusteri.Duzenle(m);

            MessageBox.Show(cevap);
            frmMusteriler f = Application.OpenForms["frmMusteriler"] as frmMusteriler;

            f.Doldur();
        }
        private void button2_Click(object sender, EventArgs e)
        {
            frmMusteriler f = new frmMusteriler();

            f.Show();
        }