private void btSimpan_Click(object sender, EventArgs e)
        {
            if (tbJudul.Text != "" && tbPengarang.Text != "" && tbPenerbit.Text != "" && tbTahunTerbit.Text != "" && tbNomorSeri.Text != "" && rbDeskripsi.Text != "")
            {
                MySqlConnection conn = this.makeDatabaseConnection();

                try
                {
                    conn.Open();

                    String sql = "INSERT INTO buku " +
                                 "(JUDUL, PENGARANG, PENERBIT, TAHUNTERBIT, NOMORSERI, HALAMAN, DESKRIPSI, GAMBAR) VALUES " +
                                 "(@judul, @pengarang, @penerbit, @tahunterbit, @nomorseri, @halaman, @deskripsi, @gambar) ";

                    MySqlCommand command = new MySqlCommand(sql, conn);


                    command.Parameters.AddWithValue("@judul", tbJudul.Text);
                    command.Parameters.AddWithValue("@pengarang", tbPengarang.Text);
                    command.Parameters.AddWithValue("@penerbit", tbPenerbit.Text);
                    command.Parameters.AddWithValue("@tahunterbit", tbTahunTerbit.Text);
                    command.Parameters.AddWithValue("@nomorseri", tbNomorSeri.Text);
                    command.Parameters.AddWithValue("@halaman", tbHalaman.Text);
                    command.Parameters.AddWithValue("@deskripsi", rbDeskripsi.Text);
                    command.Parameters.AddWithValue("@gambar", "buku.jpg");

                    int affectedRows = command.ExecuteNonQuery();//nonquery karena tidak mengambil data tapi mengirimkan data

                    conn.Close();

                    DialogResult d = MessageBox.Show("data berhasil disimpan", "", MessageBoxButtons.OK);
                    if (d == DialogResult.OK)
                    {
                        tbJudul.Text       = "";
                        tbPengarang.Text   = "";
                        tbNomorSeri.Text   = "";
                        tbPenerbit.Text    = "";
                        tbHalaman.Text     = "";
                        rbDeskripsi.Text   = "";
                        tbTahunTerbit.Text = "";

                        this.Hide();
                        formParent.refresh_data_buku();
                        formParent.show_form();
                    }
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message);
                }
            }
            else
            {
                MessageBox.Show("Semua field harus diisi");
            }
        }
        private void btSimpan_Click(object sender, EventArgs e)
        {
            DialogResult dr = MessageBox.Show("Simpan perubahan?", "Info", MessageBoxButtons.YesNo);

            if (dr == DialogResult.Yes)
            {
                MySqlConnection conn = this.makeDatabaseConnection();

                try
                {
                    conn.Open();

                    String sql = "UPDATE buku " +
                                 "SET JUDUL = @judul, " +
                                 "PENGARANG = @pengarang, " +
                                 "PENERBIT = @penerbit, " +
                                 "TAHUNTERBIT = @tahunterbit, " +
                                 "NOMORSERI = @nomorseri, " +
                                 "HALAMAN = @halaman, " +
                                 "DESKRIPSI = @deskripsi, " +
                                 "GAMBAR = @gambar " +
                                 "WHERE ID_BUKU = @id";

                    MySqlCommand command = new MySqlCommand(sql, conn);

                    command.Parameters.AddWithValue("@judul", tbJudul.Text);
                    command.Parameters.AddWithValue("@pengarang", tbPengarang.Text);
                    command.Parameters.AddWithValue("@penerbit", tbPenerbit.Text);
                    command.Parameters.AddWithValue("@tahunterbit", tbTahunTerbit.Text);
                    command.Parameters.AddWithValue("@nomorseri", tbNomorSeri.Text);
                    command.Parameters.AddWithValue("@halaman", tbHalaman.Text);
                    command.Parameters.AddWithValue("@deskripsi", rbDeskripsi.Text);
                    command.Parameters.AddWithValue("@gambar", "buku.jpg");
                    command.Parameters.AddWithValue("@id", this.id);

                    int affectedRows = command.ExecuteNonQuery();//nonquery karena tidak mengambil data tapi mengirimkan data

                    conn.Close();

                    DialogResult d = MessageBox.Show("data berhasil disimpan", "", MessageBoxButtons.OK);
                    if (d == DialogResult.OK)
                    {
                        tbJudul.Text       = "";
                        tbPengarang.Text   = "";
                        tbNomorSeri.Text   = "";
                        tbPenerbit.Text    = "";
                        tbHalaman.Text     = "";
                        rbDeskripsi.Text   = "";
                        tbTahunTerbit.Text = "";

                        this.Hide();
                        formParent.refresh_data_buku();
                        formParent.show_form();
                    }
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message);
                }
            }
        }