C# Oracle 插入出问题``求教高手 - .NET技术 / C#

C# code:
private void savBtn_Click(object sender, EventArgs e)
{
string sql;
try
{
conn.Open();
if (ticketNum != "")
{
MessageBox.Show("adasdfasdfsafdsafadasdfas");
sql = "update";
}
else
{
if (ticNumExtBox.Text == null)
{
MessageBox.Show("ticketNum can not be null");
}
else
{
sql = "insert into ticket(_ticknum_ext,_subject,_comments,_date_time,_domain,_site,_sector,_channel,_creator_team,_destination_team,_language,_creator,_skill,_treating_agent,_status,_type,_customer,_dossier_ref_num,_called_num) values ('" +
ticNumExtBox.Text + "','" +
subjectBox.Text + "','" +
dateTimePicker1.Value + "','" +
domainBox.Text + "','" +
siteBox.Text + "','" +
sectorBox.Text + "','" +
channelCom.Text + "','" +
cTBox