how to check succeeded and failed sending a message in gsmcomm library

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C#

Oracle

GSM

i build a simple application for sending message using gsmcomm library and C#. when i sent message through a modem i store it to oracle database SENTMESSAGE table. I provide a table when sending message failed namely FAILEDMESSAGE table (ID, DATE, TIME, PHONENUMBER, MESSAGE), but i still didn't understand how implemented it.

Anyone can suggest me how to differentiate between sending a message succeeded and failed in gsmcomm library?

this is my code for sending a message :

private void btnSentSMS_Click(object sender, EventArgs e)
{
    var msg = txtMessage.Text;
    var phoneNumber = txtNumber.Text;
    var pdu = new SmsSubmitPdu(msg, phoneNumber, string.Empty);
    comm.SendMessage(pdu);
    MessageBox.Show("sms sent");

    //STORE SEND SMS TO DATABASE
    OracleCommand cmd = new OracleCommand();
    cmd.CommandText = @"INSERT INTO SENTMESSAGE (ID, DATE, TIME, PHONENUMBER, MESSAGE) VALUES 
                       (SQ_SENTMESSAGE.NEXTVAL, '" + DateTime.Now + "', TO_DATE('" + DateTime.Now + "', 'dd/MM/yyyy hh24:mi:ss'), '"
                        + phoneNumber + "', '" + msg + "')";
    cmd.Connection = koneksi_manual.con;
    koneksi_manual.con.Open();// <= Open connection before executing the command.
    cmd.ExecuteNonQuery();
    koneksi_manual.con.Close(); //closing connection
}