how to auto compelete datagridview ?

Question

 

 

i wan to make columns "kode Barang " get value data from database and then columns "nama Barang" auto compelete.

 

private void _auto()
        {
            string str;
            conn = config.Connetion;
            conn.Open();
            try
            {
                str = "SELECT * FROM db_stok where kode_barang = '" + DG_masuk.Rows[3].Cells[3].Value.ToString() + "'";
                CMD = new MySqlCommand(str, conn);
                dr = CMD.ExecuteReader();

                while (dr.Read())
                {
                    string nama_barang = dr.GetValue(1).ToString();
                    DG_masuk.Rows[4].Cells[4].Value = nama_barang;
                }
            }

            catch (Exception ex)
            {
                MessageBox.Show("erorr!!" + ex.Message);
            }
        }