Backgroundworker.CancelAsync() 不起作用

本文关键字：不起作用 CancelAsync Backgroundworker | 更新日期: 2023-09-27 18:33:28

我有一个运行单个进程的后台工作者。我希望能够在处理过程中取消处理，但是当我调用 CancelAsync（） 方法时，它实际上永远不会取消。我错在哪里？

下面是 DoWork（） 方法：

        private void bgw_DoWork(object sender, DoWorkEventArgs e)
    {
        BackgroundWorker b = sender as BackgroundWorker;
        if (b != null)
        {
             if (!b.CancellationPending)
            {
                try
                {
                    // Let's run the process as a backgroundworker so we have the ability to cancel the search, and/or be able to view results while it's still searching
                    ProcessParameters pp = e.Argument as ProcessParameters;
                    if (pp.DoReplace)
                        results = FindReplace.FindReplace.FindAndReplace(pp.PathToSearch, pp.FindText, pp.ReplaceText, pp.UseRegularExpressions, pp.IncludeList, pp.ExcludeList, pp.RecurseSubdirectories, pp.IgnoreCase);
                    else
                        results = FindReplace.FindReplace.Find(pp.PathToSearch, pp.FindText, pp.UseRegularExpressions, pp.IncludeList, pp.ExcludeList, pp.RecurseSubdirectories, pp.IgnoreCase);
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.ToString());
                }
            }
            else
            {
                // Cancel was clicked
                e.Cancel = true;
            }
        }
    }

以下是开始处理的方法：

        private void btnGo_Click(object sender, EventArgs e)
    {
        if (btnGo.Text == "Cancel")
        {
            if (DialogResult.Yes == MessageBox.Show("Are you sure you wish to cancel?", "Cancel Requested", MessageBoxButtons.YesNo, MessageBoxIcon.Question))
                bgw.CancelAsync();
            return;
        }
        if (tbFind.Text.Length == 0)
        {
            MessageBox.Show("Find text is not valid.");
            return;
        }
        tbFound.Text = String.Empty;
        tbFoundInThisFile.Text = String.Empty;
        lvResults.Items.Clear();
        includeList = null;
        excludeList = null;
        results = null;
        if (radDirectory.Checked && !radFile.Checked)
        {
            includeList = BuildIncludeExcludeList(tbIncludeFiles.Text);
            excludeList = BuildIncludeExcludeList(tbExcludeFiles.Text);
        }
        ProcessParameters pp = null;
        if (chkReplace.Checked)
            pp = new ProcessParameters(tbPath.Text, tbFind.Text, tbReplace.Text, chkUseRegEx.Checked, includeList, excludeList, chkRecursion.Checked, chkIgnoreCase.Checked, true);
        else
            pp = new ProcessParameters(tbPath.Text, tbFind.Text, chkUseRegEx.Checked, includeList, excludeList, chkRecursion.Checked, chkIgnoreCase.Checked, false);
        bgw.RunWorkerAsync(pp);
        // Toggle fields to locked while it's running
        btnGo.Text = "Cancel";
    }

下面是 WorkerComplete（） 事件：

        private void bgw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        btnGo.Text = "Go";
        string message = String.Empty;
        const string caption = "FindAndReplace is Complete";
        if (!e.Cancelled)
        {
            if (results != null)
            {
                tbFound.Text = results.Found.ToString();
                tbSearched.Text = results.FilesSearched.ToString();
                tbSkipped.Text = results.FilesSkipped.ToString();
                message = String.Format("Search finished resulting in {0} match(es).", results.Found);
            }
            else
                message = "The FindAndReplace results were empty. The process was cancelled or there was an error during operation.";
        }
        else
            message = "The FindAndReplace process was cancelled.";
        if (e.Error != null)
            message += String.Format("{0}{0}There was an error during processing: {1}", Environment.NewLine, e.Error);
        MessageBox.Show(message, caption);
    }

Backgroundworker.CancelAsync() 不起作用

CancelAsync实际上不会中止您的线程或类似的东西 那。它向工作线程发送一条消息，指出工作应该是 通过后台工作者取消。你的做工 在后台运行的委托必须定期检查 这家酒店并自行处理取消。

在此处阅读更多内容

您实际上没有办法取消该操作。 问题是这段代码

               if (pp.DoReplace)
                    results = FindReplace.FindReplace.FindAndReplace(pp.PathToSearch, pp.FindText, pp.ReplaceText, pp.UseRegularExpressions, pp.IncludeList, pp.ExcludeList, pp.RecurseSubdirectories, pp.IgnoreCase);
                else
                    results = FindReplace.FindReplace.Find(pp.PathToSearch, pp.FindText, pp.UseRegularExpressions, pp.IncludeList, pp.ExcludeList, pp.RecurseSubdirectories, pp.IgnoreCase);

一旦开始运行，就没有任何方法可以中断。 因此，最终发生的是你点击了取消，但取消永远不会注册，除非您在操作开始之前取消了。 该操作完成后，DoWork 方法将成功返回，并且后台工作线程永远不会触发取消。

编辑：如果您有办法将文本分解为较小的块，然后可以"搜索和替换"，则可以循环访问这些片段并在每个循环中执行取消检查。 但是，您需要确保考虑搜索字符串跨越这些中断边界，因此实际上可能需要更长的时间才能允许取消。

你的代码是正确的，但如果你再仔细阅读一遍，你会发现一旦后台工作线程启动，它很快就会超越取消检查。之后，即使您尝试取消，它也将不再起作用。

您必须重新设计搜索和替换算法以包括取消检查，以便根据需要支持取消。

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