How to Make Autocomplete from database sql?

Question

This my code in class Fungsi

public void autocompele1(TextBox autotext)
        {
            conn = Koneksi.Conn;
            conn.Open();
            cmd = new SqlCommand("SELECT Nama_Barang FROM Tb_Barang ORDER BY Nama_Barang", conn);
            try
            {

                Reader = cmd.ExecuteReader();
                if(Reader.HasRows)
                {
                    while (Reader.Read())
                    {
                        autotext.AutoCompleteCustomSource.Add(Reader["Nama_Barang"].ToString());
                    }
                }
                else
                {
                    MessageBox.Show("Data Not Found");
                }
            }
            catch(Exception ex)
            {
                MessageBox.Show("erorr" + ex.Message);
            }

            finally
            {
                conn.Close();
                Reader.Close();
            }

        }

 and i called in form like this 

 

private void Form_Transaksi_Load(object sender, EventArgs e)
        {
            Fungsi auto = new Fungsi();
            auto.autocompele1(txt_NamaBarang);
        }