C#BackgroundWorker 不工作

Question

我正在尝试让这个BackgroundWorker 工作。当您单击“查看订单”按钮时，它将显示一条类似于“检索新订单...”等的消息，并将执行后台工作（mysql 查询），现在，DoWork 方法中有一堆东西，并且一切都没有完成。

我知道这不是因为 MySQL 查询，因为它无需后台工作人员即可自行正常工作。

这是代码：

private void ViewOrders_Click(object sender, EventArgs e)
        {
            SlideTimer.Enabled = true;
            Alert("Retrieving unconfirmed orders. Please wait.",
                "Cancel",
                Information,
                true,
                Color.FromArgb(63, 187, 249)
            );
            action = Action.ViewOrder;

            bWorker.WorkerSupportsCancellation = true;
            bWorker.DoWork += new DoWorkEventHandler(bWorker_DoWork);
            bWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bWorker_RunWorkerCompleted);

            bWorker.RunWorkerAsync();
        }

        void bWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            SlideTimer.Enabled = true;
            Alert("All unconfirmed orders have been retrieved.",
                "Dismiss",
                Information,
                true,
                Color.FromArgb(63, 187, 249)
            );
            action = Action.None;
        }

        void bWorker_DoWork(object sender, DoWorkEventArgs e)
        {
            // Connect to Database, check for orders, and end.
            if (bWorker.CancellationPending == true)
            {
                e.Cancel = true;
            }
            else
            {
                if (action == Action.ViewOrder)
                {
                    thelist.Clear();
                    thelist.Visible = true;
                    thelist.BringToFront();
                    MessageBox.Show("");
                    thelist.Columns.Add("Order #");
                    thelist.Columns.Add("Name");
                    thelist.Columns.Add("E-mail Address");
                    thelist.Columns.Add("Delivery Address");
                    thelist.Columns.Add("Company");
                    thelist.Columns.Add("Phone Number");

                    // Check for new orders.
                    MySql.Data.MySqlClient.MySqlConnection msc = new MySql.Data.MySqlClient.MySqlConnection(cs);
                    try
                    {
                        msc.Open();

                        // Check for orders now.
                        string st = "SELECT DISTINCT(sessionid), firstname, lastname, email, streetaddress, suburb, postcode, state, company, phone FROM mysql_9269_dbase.order";
                        MySql.Data.MySqlClient.MySqlCommand cd = new MySql.Data.MySqlClient.MySqlCommand(st, msc);
                        MySql.Data.MySqlClient.MySqlDataReader msdr = cd.ExecuteReader();

                        while (msdr.Read())
                        {
                            if (thelist.Items.Count == 0)
                            {
                                ListViewItem LItem = new ListViewItem(msdr[0].ToString());
                                ListViewItem.ListViewSubItemCollection SubItems = new ListViewItem.ListViewSubItemCollection(LItem);

                                SubItems.Add(msdr[1].ToString() + " " + msdr[2].ToString());
                                SubItems.Add(msdr[3].ToString());
                                SubItems.Add(msdr[4].ToString() + " " + msdr[5].ToString() + " " + msdr[6].ToString() + " " + msdr[7]);
                                SubItems.Add(msdr[8].ToString());
                                SubItems.Add(msdr[9].ToString());

                                thelist.Items.Add(LItem);

                                thelist.Update();
                            }
                            else
                            {
                                sound.Play();

                                //status.Text = "Records found; Retrieving now.";
                                var found = false;

                                foreach (var item in thelist.Items)
                                {
                                    if (item.ToString().Contains(msdr[0].ToString()))
                                        found = true;
                                }
                                if (thelist.Items.Count == 0 || !found)
                                {
                                    ListViewItem LItem = new ListViewItem(msdr[0].ToString());
                                    ListViewItem.ListViewSubItemCollection SubItems = new ListViewItem.ListViewSubItemCollection(LItem);

                                    SubItems.Add(msdr[1].ToString() + " " + msdr[2].ToString());
                                    SubItems.Add(msdr[3].ToString());
                                    SubItems.Add(msdr[4].ToString() + " " + msdr[5].ToString() + " " + msdr[6].ToString() + " " + msdr[7]);
                                    SubItems.Add(msdr[8].ToString());
                                    SubItems.Add(msdr[9].ToString());

                                    thelist.Items.Add(LItem);

                                    thelist.Update();
                                }
                            }
                        }
                    }
                    catch (Exception en)
                    {
                        Alert(en.Message,
                            "Retry",
                            Error,
                            true,
                            Color.FromArgb(249, 87, 55)
                        );
                    }
                    msc.Close();

                }
                thelist.Visible = true;
                thelist.BringToFront();
            }
        }

        private void MessageLink_Click(object sender, EventArgs e)
        {
            switch (MessageLink.Text)
            {
                case "Cancel":
                    bWorker.CancelAsync();

                    SlideTimer.Enabled = true;
                    Alert("You have successfully cancelled the current operation.",
                        "Dismiss",
                        Information,
                        true,
                        Color.FromArgb(63, 187, 249)
                    );
                    action = Action.None;
                    break;
                case "":
                    break;
                default:
                    break;
            }
        }

没有错误或任何东西。只是什么也没发生。是什么导致后台（所谓的）Worker 不执行 DoWork() ？

*抱歉冗长的代码片段。

Answer 1

您已连接回调，但实际上并未调用 RunWorkerAsync 来启动它。

顺便说一句，您还在 DoWork 方法中调用 UI 元素，这将失败。您需要使用 BeginInvoke 将更新合并回 UI 线程，或者在 RunWorkerComplete 方法（自动在 UI 线程上运行）中执行更新。

Answer 2

MessageBox.Show("");

这会造成一个大问题。

您无法从非 UI 线程调用 UI。我很惊讶它没有引发异常。充其量它可能会导致您的线程中止并且不执行任何操作。

theList 看起来也像一个 UI 元素。如果您要添加控件，那么您需要通过事件将数据传递到 UI，以便您可以在那里更新它。

您还可以：

Alert(en.Message,
    "Retry",
    Error,
    true,
    Color.FromArgb(249, 87, 55)
);

在您的异常处理程序中。这看起来又像是您正在尝试调用 UI 元素。