private void btn_edit_Click(object sender, EventArgs e)
        {
            var baris = dgv_data_buku.CurrentRow.Index;

            string[] data = book.get_buku(dgv_data_buku.Rows[baris].Cells[0].Value.ToString());

            buku_form book_form = new buku_form(this);

            book_form.label_header.Text  = "Edit Buku";
            book_form.btn_update.Visible = true;
            book_form.btn_tambah.Visible = false;
            book_form.txt_id.ReadOnly    = true;
            book_form.txt_id.Text        = data[0];
            book_form.txt_judul.Text     = data[1];
            book_form.txt_pengarang.Text = data[2];
            book_form.txt_penerbit.Text  = data[3];
            book_form.txt_tahun.Text     = data[4];
            book_form.cmb_kategori.Text  = data[6];
            book_form.txt_stok.Text      = data[5];
            book_form.ShowDialog();
        }
        private void btn_tambah_Click(object sender, EventArgs e)
        {
            buku_form book_form = new buku_form(this);

            book_form.ShowDialog();
        }