我有一个示例 WinForms 应用程序,它使用BackgroundWorker
成分。它工作正常,但是当我点击Cancel
按钮取消后台线程,但它不会取消线程。当我击中Cancel
呼叫按钮.CancelAsync()
方法,然后在RunWorkerCompleted
事件处理程序e.Cancelled
财产永远存在false
。我想当我击中Cancel
按钮应将其设置为 true。
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
for (int i = 1; i <= 100; i++)
{
// Wait 100 milliseconds.
Thread.Sleep(100);
// Report progress.
if (backgroundWorker1.CancellationPending == true)
{
//label1.Text = "Cancelled by user.";
break;
}
backgroundWorker1.ReportProgress(i);
}
}
private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
// Change the value of the ProgressBar to the BackgroundWorker progress.
progressBar1.Value = e.ProgressPercentage;
// Set the text.
label1.Text = e.ProgressPercentage.ToString();
}
private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
if (e.Cancelled == true)
{
label1.Text = "Canceled!";
}
else if (e.Error != null)
{
label1.Text = "Error: " + e.Error.Message;
}
else
{
label1.Text = "Done!";
}
}
private void button2_Click(object sender, EventArgs e)
{
if (backgroundWorker1.WorkerSupportsCancellation == true)
{
// Cancel the asynchronous operation.
backgroundWorker1.CancelAsync();
}
}
Canceled 属性仍然为 false,因为您跳出了循环,然后允许后台工作程序的 DoWork 函数以正常方式结束。您永远不会告诉您的后台工作人员组件挂起的取消实际上已被接受。
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
for (int i = 1; i <= 100; i++)
{
// Wait 100 milliseconds.
Thread.Sleep(100);
if (backgroundWorker1.CancellationPending)
{
e.Cancel = true;
break;
}
// Report progress.
backgroundWorker1.ReportProgress(i);
}
}
这种区别很重要,因为有时您可能希望在检测到 CancellationPending 请求时回滚已经完成的工作,因此可能需要一段时间才能真正完成取消。
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