private void btn_MusteriEkle_Click(object sender, EventArgs e)
        {
            Form_Musteri musteri = new Form_Musteri();

            musteri.ShowDialog();
        }
        private void dg_Musteriler_DoubleClick(object sender, EventArgs e)
        {
            Form_Musteri musteri = new Form_Musteri(MusteriId);

            musteri.ShowDialog();
        }