BackgroundWorker.CancelAsync Метод - это то, что вам нужно. Здесь является хорошим примером для вас.
Если у вас есть трудоемкий процесс, вам придется использовать отдельный поток для его обработки, чтобы поддержать отмену.Если вы выполните этот трудоемкий процесс в главном потоке (потоке пользовательского интерфейса), он будет занят и не примет ваш запрос на отмену до тех пор, пока не выполнит эту задачу.Вот почему вы испытываете зависание пользовательского интерфейса.
Если вы используете backgroundWorker для выполнения задачи, требующей много времени, и если вы отметили флаг CancellationPending в методе BackgroundWorker.DoWork, вы можете достичь того, чего хотите.
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
namespace BackgroundWorker
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
//mandatory. Otherwise will throw an exception when calling ReportProgress method
backgroundWorker1.WorkerReportsProgress = true;
//mandatory. Otherwise we would get an InvalidOperationException when trying to cancel the operation
backgroundWorker1.WorkerSupportsCancellation = true;
}
//This method is executed in a separate thread created by the background worker.
//so don't try to access any UI controls here!! (unless you use a delegate to do it)
//this attribute will prevent the debugger to stop here if any exception is raised.
//[System.Diagnostics.DebuggerNonUserCodeAttribute()]
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
//NOTE: we shouldn't use a try catch block here (unless you rethrow the exception)
//the backgroundworker will be able to detect any exception on this code.
//if any exception is produced, it will be available to you on
//the RunWorkerCompletedEventArgs object, method backgroundWorker1_RunWorkerCompleted
//try
//{
DateTime start = DateTime.Now;
e.Result = "";
for (int i = 0; i < 100; i++)
{
System.Threading.Thread.Sleep(50); //do some intense task here.
backgroundWorker1.ReportProgress(i, DateTime.Now); //notify progress to main thread. We also pass time information in UserState to cover this property in the example.
//Error handling: uncomment this code if you want to test how an exception is handled by the background worker.
//also uncomment the mentioned attribute above to it doesn't stop in the debugger.
//if (i == 34)
// throw new Exception("something wrong here!!");
//if cancellation is pending, cancel work.
if (backgroundWorker1.CancellationPending)
{
e.Cancel = true;
return;
}
}
TimeSpan duration = DateTime.Now - start;
//we could return some useful information here, like calculation output, number of items affected, etc.. to the main thread.
e.Result = "Duration: " + duration.TotalMilliseconds.ToString() + " ms.";
//}
//catch(Exception ex){
// MessageBox.Show("Don't use try catch here, let the backgroundworker handle it for you!");
//}
}
//This event is raised on the main thread.
//It is safe to access UI controls here.
private void backgroundWorker1_ProgressChanged(object sender,
ProgressChangedEventArgs e)
{
progressBar1.Value = e.ProgressPercentage; //update progress bar
DateTime time = Convert.ToDateTime(e.UserState); //get additional information about progress
//in this example, we log that optional additional info to textbox
txtOutput.AppendText(time.ToLongTimeString());
txtOutput.AppendText(Environment.NewLine);
}
//This is executed after the task is complete whatever the task has completed: a) sucessfully, b) with error c)has been cancelled
private void backgroundWorker1_RunWorkerCompleted(object sender,
RunWorkerCompletedEventArgs e)
{
if (e.Cancelled) {
MessageBox.Show("The task has been cancelled");
}
else if (e.Error != null)
{
MessageBox.Show("Error. Details: " + (e.Error as Exception).ToString());
}
else {
MessageBox.Show("The task has been completed. Results: " + e.Result.ToString());
}
}
private void btoCancel_Click(object sender, EventArgs e)
{
//notify background worker we want to cancel the operation.
//this code doesn't actually cancel or kill the thread that is executing the job.
backgroundWorker1.CancelAsync();
}
private void btoStart_Click(object sender, EventArgs e)
{
backgroundWorker1.RunWorkerAsync();
}
}
}