Cross-thread operation not valid: Control 'Form2' accessed from a thread other than the thread it was created on

Question

I have 2 Forms, in Form1 , there are a lot of transaction to be done, so i have used the BackgroundWorker. so during the action to be taken i want the form2 to be opened and shows the progressbar ( the progress of the actions ) so I have done like this:

This is Form1

public partial class Form1 : Form
{
    Form2 form2 = new Form2();
    public Form1()
    {
        InitializeComponent();
        Shown += new EventHandler(Form1_Shown);

        // To report progress from the background worker we need to set this property
        backgroundWorker1.WorkerReportsProgress = true;
        // This event will be raised on the worker thread when the worker starts
        backgroundWorker1.DoWork += new DoWorkEventHandler(backgroundWorker1_DoWork);
        // This event will be raised when we call ReportProgress
        backgroundWorker1.ProgressChanged += new ProgressChangedEventHandler(backgroundWorker1_ProgressChanged);
    }

    void Form1_Shown(object sender, EventArgs e)
    {
        form2.Show();
        // Start the background worker
        backgroundWorker1.RunWorkerAsync();

    }


    private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
    {
        // Your background task goes here
        for (int i = 0; i <= 100; i++)
        {
            // Report progress to 'UI' thread
            backgroundWorker1.ReportProgress(i);
            // Simulate long task
            System.Threading.Thread.Sleep(100);
        }
        form2.Close();
    }


    private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
    {
        // The progress percentage is a property of e
        form2.progressBar1.Value = e.ProgressPercentage;
    }
}

I have a Progressbar in form2 which its modifier is public. the problem is that when the actions would be accompilshed the form2 ( which contans the progress bar) should be closed , So i used

    form2.Close();

but i get this error message

  Cross-thread operation not valid: Control 'Form2' accessed from a thread other than the thread it was created on

how can i solve this problem?

You will need to put `form2.Close()` into `backgroundWorker1.RunWorkerCompleted` event handler. — Kirill Shlenskiy, Sep 23 '14 at 05:27
This question is answered on StackOverflow at least a few times a day. I have marked this at a duplicate of a single one - however, feel free to click through all of the related ones that are the same issue. — Simon Whitehead, Sep 23 '14 at 05:32

score 2 · Answer 1 · answered Sep 23 '14 at 05:30

2

Use delegate to make it thread safe

 if(form2.InvokeRequired)
    {
        form2.Invoke(new MethodInvoker(delegate { form2.Close() }));
    }

answered Sep 23 '14 at 05:30

Dark Knight

3,507
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score 0 · Answer 2 · edited May 23 '17 at 12:30

0

The problem is the control just can be accessed by the thread that create it.

Check this:

http://msdn.microsoft.com/en-us/library/ms171728.aspx

And this :

Cross-thread operation not valid: Control 'Form2' accessed from a thread other than the thread it was created on

edited May 23 '17 at 12:30

Community

1
1

answered Sep 23 '14 at 05:24

Ollie Strevel

861
1
14
27

Cross-thread operation not valid: Control 'Form2' accessed from a thread other than the thread it was created on

2 Answers2