Problem with BackgroundWorker component?

Question

Problem with BackgroundWorker component?

Ken Ekholm 151

When I pushed the Transfer button a second time, I get the this error message, System.InvalidOperationException: 'This BackgroundWorker is currently busy and cannot run multiple tasks concurrently.' Can someone help me with this problem?

 private void buttonTransfer_Click(object sender, EventArgs e)
 {
       if (backgroundWorker1.IsBusy)
       {
            backgroundWorker1.WorkerSupportsCancellation = true
``          backgroundWorker1.CancelAsync();
            MessageBox.Show("Running!");
        }

         richTextBoxViewStatus.Clear();                  
         backgroundWorker1.WorkerReportsProgress = true;
        backgroundWorker1.RunWorkerAsync();
}




private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            backgroundWorker1.WorkerSupportsCancellation = true;
            backgroundWorker1.CancelAsync();
        }


private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
      do some work
}

5 answers

Your answer

Answer 1

@Ken Ekholm , Welcome to Microsoft Q&A, based on your code, I can reproduce your problem.

Please don't start the BackgroundWorker twice because One BackgroundWorker can only run One task.

If you want to run many background tasks at the same time, you could create multiple BackgroundWorker objects.

I make a code examaple for two background tasks and you could refer to it.

Hope this could help you.

Update code:

Best Regards,
Jack

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Answer 2

Ken Ekholm 151

Is it possible to "reuse" the same backgroundworker instead for creating a new one?

Jack J Jun 25,296 Reputation points

2022-04-14T07:03:10.187+00:00

@Ken Ekholm , Sorry for the late response, now I have updated my code for reusing the same backgroundworker to enable or disable the start button.

Answer 3

Karen Payne MVP 35,586 Volunteer Moderator

Try the following, fill in the TODO sections

private void RunButton_Click(object sender, EventArgs e)
{
    var bw = new BackgroundWorker { WorkerReportsProgress = true };
    bw.DoWork += (_, _) => {/* TODO  */ };
    bw.ProgressChanged += (_, _) => {/* TODO  */ };
    bw.RunWorkerCompleted += (_, _) => {/* TODO  */ };
    bw.RunWorkerAsync();
}

Answer 4

Ken Ekholm 151

This code require language C# 9.0 and I have for the moment language C# 7.3.
How do I write the same code for langauge C# 7.3?

I have tried to update to language C# 9.0 without success.

Karen Payne MVP 35,586 Volunteer Moderator

Take your pick, the main differences is I used discards verses conventional subscription to events.

Discards started with C# 7

Starting with C# 7.0, C# supports discards, which are placeholder variables that are intentionally unused in application code. Discards are equivalent to unassigned variables; they don't have a value.

public partial class Form1 : Form  
{  
    public Form1()  
    {  
        InitializeComponent();  
    }  
  
    private void RunButton_Click(object sender, EventArgs e)  
    {  
        var bw = new BackgroundWorker { WorkerReportsProgress = true };  
        bw.DoWork += BwOnDoWork;  
        bw.ProgressChanged += delegate(object o, ProgressChangedEventArgs args) {  /* TODO  */ };  
        bw.RunWorkerCompleted += (o, args) => { /* TODO  */};  
        bw.RunWorkerAsync();  
    }  
  
    private void BwOnDoWork(object sender, DoWorkEventArgs e)  
    {  
        /* TODO  */  
    }  
}

Answer 5

Ken Ekholm 151

Edit: I managed to update to language C# 9.0.
But it does not work to "reuse" the same backgroundworker with this code.

private void RunButton_Click(object sender, EventArgs e)
{
var bw = new BackgroundWorker { WorkerReportsProgress = true };
bw.DoWork += (_, ) => {/* TODO */ };
bw.ProgressChanged += (, ) => {/* TODO */ };
bw.RunWorkerCompleted += (, _) => {/* TODO */ };
bw.RunWorkerAsync();
}

Is it possible to resolve this?

Karen Payne MVP 35,586 Reputation points Volunteer Moderator

2022-04-10T23:59:01.927+00:00

But it does not work to "reuse" the same backgroundworker with this code

My code was not meant to run a single BackGroundWorker and is unwise.

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Problem with BackgroundWorker component?

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