BackGroundworker Cancelation not working for wbadmin.exe

Question

Ok, I am Using: C# with Windows Forms

I have a backgroundwork, which works. Now I wanted to create a cancellation button, but even though I told it to cancel and the backgroundwork accepts that, it continues to run the executable it triggers.

I have a cancel button with following code

private void cancelBackup_Click(object sender, EventArgs e)
    {
        backgroundWorker1.CancelAsync();
        displayResults.Text = "Operation Cancelled";

    }

And the background worker code is here:

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
    {
        String invoer = comboboxDriveLetter.Text;
        invoer = invoer.Remove(2);

        ProcessStartInfo pStartInfo = new ProcessStartInfo("C:\\windows\\system32\\wbadmin.exe", " START BACKUP -backuptarget:" + invoer + " -include:c: -AllCritical -quiet");

        pStartInfo.CreateNoWindow = true;
        pStartInfo.UseShellExecute = false;
        pStartInfo.RedirectStandardInput = true;
        pStartInfo.RedirectStandardOutput = true;
        pStartInfo.RedirectStandardError = true;

        Process process1 = new Process();

        process1.OutputDataReceived += new DataReceivedEventHandler(OutputHandler);
        process1.ErrorDataReceived += new DataReceivedEventHandler(ErrorHandler);
        pStartInfo.Verb = "runas";
        process1.StartInfo = pStartInfo;
        process1.SynchronizingObject = displayResults;

        process1.Start();
        process1.BeginOutputReadLine();


        process1.WaitForExit();
    }

When I click the button to cancel, it goes through the action, but the backup just continues, as the richtextbox ends up displaying the entire thing

Operation CancelledCreating a shadow copy of the volumes specified for backup...
Creating a shadow copy of the volumes specified for backup...
Creating a shadow copy of the volumes specified for backup...
Creating a shadow copy of the volumes specified for backup...
The backup of volume SYSTEM (1.99 GB) successfully completed.
Creating a backup of volume OS(C:), copied (0%).
Creating a backup of volume OS(C:), copied (0%).
Creating a backup of volume OS(C:), copied (8%).
Creating a backup of volume OS(C:), copied (55%).
Creating a backup of volume OS(C:), copied (82%).
The backup of volume OS(C:) successfully completed.
The backup operation successfully completed.
Summary of the backup operation:
------------------
The backup of volume SYSTEM (1.99 GB) successfully completed.
The backup of volume OS(C:) successfully completed.

What am I doing wrong?

Answer 1

The cancellation of BackgroundWorker is cooperative. That means that the code inside DoWork should periodically check a flag and quit when requested.

And process1.Start(); will of course not respond to that flag.

You could try calling process1.Kill(); from the Cancel button but I'm not sure whether that is thread-safe.

So probably this:

//process1.WaitForExit();
while (! process1.WaitForExit(100))
{
    if (bgw.CancellationPending)
    {
       e.cancel = true;
       process1.Kill();
    }
}