试图减去两次以节省时间

Question

我想把时间减去C＃代码

    cmd.CommandText = "update TECHNOVA_SMS_TICKET set ISSUE_STATUS='" + statuchange + "' , SMS_CLOSED_TIME= '" + closedTime.Text + "' , SMS_TIME_SPENT= '+ NVL(24 * (to_date(" + closedTime.Text + ",'MM/DD/YYYY HH:MI:SS PM') - to_date(" + currecT + ",'MM/DD/YYYY HH:MI:SS PM')),0)' where SMS_TICKET_ID='" + issueId + "'";
    cmd.ExecuteNonQuery();  

    issueclosedsucess.Text = " Issue is Closed. Acknowlege!";
    issueclosedsucess.ForeColor = System.Drawing.Color.Green;

    dashboardissue();

错误是附加信息：外部组件抛出异常。