C#循环查询出现错误

Question

你想在线程里更新UI,需要使用委托.搜一搜:委托操作UI
如果你是在forms.timer里更新,是没有问题的.
但是如果你在system.timers.timer里更新,这是个线程,必须使用委托

Answer 1

        private void auto_print()
        {
            checkNewOrder_printcon_auto = new MySqlConnection(strConn);
            DataTable dtCheckNewOrderTb = new DataTable();
            DataTable getserviceTimetb = new DataTable();
            DateTime dtNow = DateTime.Now;
            DateTime dtTime10 = dtNow.AddSeconds(10f);
            string checkOrderSql = "";
            //int timenow = 0;            try
            {
                dtNow = getNow_auto();
                MessageBox.Show("新订单自动打印功能已开启!");
                DateTime dtpast = dtNow;
                for (int i = 0; i < 1; i = 0)
                {
                    if (checkNewOrder_printcon_auto.State != ConnectionState.Open)
                    {
                        checkNewOrder_printcon_auto.Open();
                    }
                    if (dtpast == dtNow)
                       //checkOrderSql = "select y.order_id from shop_order y where from_unixtime(y.ceart_time) <='" + dtNow + "' and from_unixtime(y.ceart_time)>date_add('" + dtNow + "',interval '-10' second)  and y.order_state!='0' and y.order_state!='10' and y.order_state!='50' and liushuixian='" + liushuixian.Text.ToString() + "'";
                        checkOrderSql = "select y.order_id from shop_order y where from_unixtime(y.ceart_time) <='" + dtNow + "' and from_unixtime(y.ceart_time)>date_add('" + dtNow + "',interval '-10' second)  and y.order_state='20' and y.is_print=0 and liushuixian='" + liushuixian.Text.ToString() + "'";
                    else
                        //checkOrderSql = "select y.order_id from shop_order y where from_unixtime(y.ceart_time) <='" + dtNow + "' and from_unixtime(y.ceart_time)>'" + dtpast + "' and y.order_state!='0' and y.order_state!='10' and y.order_state!='50'  and liushuixian='" + liushuixian.Text.ToString() + "'";
                        checkOrderSql = "select y.order_id from shop_order y where from_unixtime(y.ceart_time) <='" + dtNow + "' and from_unixtime(y.ceart_time)>'" + dtpast + "' and y.order_state='20' and y.is_print=0 and liushuixian='" + liushuixian.Text.ToString() + "'";                    MySqlDataAdapter mda = new MySqlDataAdapter(checkOrderSql, checkNewOrder_printcon_auto);
                    mda.Fill(dtCheckNewOrderTb);                    if (dtCheckNewOrderTb.Rows.Count > 0)
                    {
                        for (int j = 0; j < dtCheckNewOrderTb.Rows.Count; j++)
                        {
                            orderId_auto = dtCheckNewOrderTb.Rows[j]["order_id"].ToString();
                            //this.printorder_auto();
                            //updateIsPrintStatus(orderId_auto);//更新数据库is_print为1（1为已打印）
                        }
                        dtCheckNewOrderTb.Rows.Clear();
                    }
                    
                    //callButtonEvent(dataShow, "OnClick");
                    checkNewOrder_printcon_auto.Close();
                    Thread.Sleep(10000);
                    dataShow_auto();
                    //timenow = int.Parse(((getNow_auto().Ticks - dtNow.Ticks) / 10000000).ToString());
                    dtpast = dtNow.AddMinutes(-30);
                    dtNow = getNow_auto();
                }            }