private void btnHapusBarang_Click(object sender, EventArgs e)
        {
            Barang barang = new Barang();

            barang.setId(Convert.ToInt32(txtIdBarang.Text));
            Console.WriteLine(barang.getId());
            barang.Delete();
            foreach (Control ctrl in mtpBarang.Controls)
            {
                if (ctrl is TextBox)
                {
                    ctrl.Text = "";
                }
            }
            MessageBox.Show("Barang berhasil dihapus.");
        }