C#: Cross-thread operation not valid: Control ‘progressBar1’ accessed from a thread other than the thread it was created on

Error Message: Cross-thread operation not valid: Control ‘progressBar1’ accessed from a thread other than the thread it was created on.

This goes for any control that needs to be touched by a worker thread, you cannot do it directly.  You must do a callback so the main UI thread actually does the update.

Reproduce the problem:

        private void button1_Click(object sender, EventArgs e)

        {

            progressBar1.Minimum = 0;

            progressBar1.Maximum = 100;

            System.Threading.Thread worker = new System.Threading.Thread(doWork);

            worker.Start();

        }

        private void doWork()

        {

            for (int i = 0; i < progressBar1.Maximum; i++)

            {

                progressBar1.PerformStep();

            }

        }

Solution is:

Add this method, and instead of calling progressBar1.PerformStep(), call ActuallyPerformStep():

        delegate void CallPerformStep(ProgressBar myProgressBar);

        private void ActuallyPerformStep(ProgressBar myProgressBar)

        {

            if (myProgressBar.InvokeRequired)

            {

                CallPerformStep del = ActuallyPerformStep;

                myProgressBar.Invoke(del, new object[] { myProgressBar });

                return;

            }

            myProgressBar.PerformStep();

        }

And now the main UI thread is calling the UI Control.