Background Worker Cancel Issue

lpc

17y5.6kC#

I have a method call within the background worker doWork event like this.

try
    {
          classname.method(argument, argument, argument);
    }
    catch (Exception ex)
    {
          MessageBox.Show(ex.Message);
          return;
    }

how i can implement a cancel to background worker. where to check for cancel pending. if i write the code like this

while (!bgworker.CancellationPending)
   {
         try
           {
               classname.method(argument, argument, argument);
            }
         catch (Exception ex)
           {
               MessageBox.Show(ex.Message);
              return;
            }
     }

     if (bgworker.CancellationPending
           e.Cancel = true;

then it keeps running again and again until the cancel button (bgworker.CancelAsync()) is not pressed. please help me i am new to C#. i search a lot but find examples which have loops in doWork, but i have method call.

2 Replies

Know the answer? Post it — somebody with the same question will find it here.

Benjamin Scharbach9y ago
In most cases with cancellations, you must check for the cancellations within the proper locations inside your body callbacks of the thread space. An important perception to understand is the Cancel calls normally do not force the thread to cancel. Instead, it flags that you want a cancellation and your code must force the exit inside the thread body callback.

In your code example and the other posted users code, the cancel probably would not work because it does not constantly check for the cancellation. For example, in your code you would need to check for the cancellation inside the classname.method call, because this could have a long running operation. In the other users example, their code would cancel before showing the Form, but would not be able to after the form displays.

Ben Scharbach
https://www.youtube.com/channel/UCih2aBHyGR5cJHApqkwAXBA
Danatas Gervi17y ago

Something like this:

namespace BackGrWorkCancel

{

      public partial class Form1 : Form

      {

             Classname m_worker;

             public Form1()

             {

                InitializeComponent();

                m_worker = new Classname();

                backgroundWorker1.RunWorkerAsync();



             }

             private void button1_Click(object sender, EventArgs e)

             {

                backgroundWorker1.CancelAsync();

             }

             private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)

             {

                m_worker.Method(backgroundWorker1);

             }

      }

      public class Classname

      {

             //public bool ContinueWork = true;

             public void Method(BackgroundWorker initiator)

             {

                //while (ContinueWork)

                while(initiator.CancellationPending == false)

                {

                                System.Threading.Thread.Sleep(2000);

                                Form tempForm = new Form();

                                tempForm.Show();

                }

             }

      }

}