เพิ่มข้อมูล Array c# ได้ที่แค่ครั้งเดียวไม่สามารถเพิ่มได้ทั้งหมด ท่านผู้รุ้ช่วยดูให้หน่อยครับ

private void butSave_Click(object sender, EventArgs e)
        {

            MySqlConnection connection = new MySqlConnection(MyConnectionString);
            MySqlCommand cmd;
            connection.Open();
            cmd = connection.CreateCommand();

            string[] Start = new string[12];
            Start[0] = txtStr1.Text.ToString();
            Start[1] = txtStr2.Text.ToString();
            Start[2] = txtStr3.Text.ToString();
            Start[3] = txtStr4.Text.ToString();
            Start[4] = txtStr5.Text.ToString();
            Start[5] = txtStr6.Text.ToString();
            Start[6] = txtStr7.Text.ToString();
            Start[7] = txtStr8.Text.ToString();
            Start[8] = txtStr9.Text.ToString();
            Start[9] = txtStr10.Text.ToString();
            Start[10] = txtStr11.Text.ToString();
            Start[11] = txtStr12.Text.ToString();

            string[] Finish = new string[12];
            Finish[0] = txtEnd1.Text.ToString();
            Finish[1] = txtEnd2.Text.ToString();
            Finish[2] = txtEnd3.Text.ToString();
            Finish[3] = txtEnd4.Text.ToString();
            Finish[4] = txtEnd5.Text.ToString();
            Finish[5] = txtEnd6.Text.ToString();
            Finish[6] = txtEnd7.Text.ToString();
            Finish[7] = txtEnd8.Text.ToString();
            Finish[8] = txtEnd9.Text.ToString();
            Finish[9] = txtEnd10.Text.ToString();
            Finish[10] = txtEnd11.Text.ToString();
            Finish[11] = txtEnd12.Text.ToString();

            //string[] period = new string[12];
            //period[0] = "1";
            //period[1] = "2";
            //period[2] = "3";
            //period[3] = "4";
            //period[4] = "5";
            //period[5] = "6";
            //period[6] = "7";
            //period[7] = "8";
            //period[8] = "9";
            //period[9] = "10";
            //period[10] = "11";
            //period[11] = "12";

            for (int i = 0; i < Start.Length; i++)
            {
                // Get element by index.
              //  string periods = period[i];
                string Starts = Start[i];
                string Finishs = Finish[i];
                cmd.CommandText = "INSERT INTO tb_period VALUES ('', @Starts, @Finishs)";
            //cmd.Parameters.AddWithValue("@periods", period[i].ToString());//แบบที่2
                    cmd.Parameters.AddWithValue("@Starts", Start[i].ToString());//แบบที่2
                    cmd.Parameters.AddWithValue("@Finishs", Finish[i].ToString());//แบบที่2
                    cmd.ExecuteNonQuery();
                    MessageBox.Show("คุณได้เพิ่มข้อมูลเรียบร้อยแล้ว");
                
                    connection.Close();
                }
            }