Why i get error when set value to label in new thread c#?

Question

I'm write simple application to load csv file,and in c# code start the new thread to load heavy csv file with this code:

Thread workerThread = new Thread(DoWork);
workerThread.Priority = ThreadPriority.Highest;
workerThread.Start();

and into the DoWork i try run this code:

 public void DoWork()
 {
 label1.Text = "ok";
 }

but when receive label line i get this error:

An unhandled exception of type 'System.InvalidOperationException' occurred in System.Windows.Forms.dll

Additional information: Cross-thread operation not valid: Control 'label1' accessed from a thread other than the thread it was created on.

What happen?thanks.

Your error seems to tell you: "Additional information: Cross-thread operation not valid" — Bennett Yeo, May 27 '15 at 04:02
perhaps you could:Create a void in the original thread that modifies the label. Then call the void from the other thread. — Bennett Yeo, May 27 '15 at 04:03

score 6 · Answer 1 · answered May 27 '15 at 04:12

This is a common mistake on multi-threaded app when trying to access the UI controls from a non-UI thread. Accessing UI controls from a different thread than the one creating that control is not allowed. I normally turn the invocation from non-UI thread to the UI thread by using this:

    private void DoWork()
    {
        if (label1.InvokeRequired)
        {
            // this will be called by the non-UI thread
            label1.Invoke(new Action(DoWork));
        }
        else
        {
            // the actual implementation of the DoWork method, this will be called by the UI thread
            label1.Text = "Ok";
        }
    }

Why i get error when set value to label in new thread c#?

1 Answers1