InvalidOperationException: Cross-thread operation not valid: Control ‘Form1’ accessed from a thread other than the thread it was created on.

When I first time met with this error, it was caused by an update of a windows form control from a separate thread.

Here is the workaround.

// delegation to cross the thread boundary
private delegate void AddComboBoxItemDelegate(object item);

private void AddComboBoxItem(object item)
{
  if (this.comboBox1.InvokeRequired) {
    // Invoke delegate so that the main UI thread is able to update the controls in the form
this.comboBox1.Invoke(new AddComboBoxItemDelegate(this.AddComboBoxItem), item);
  }
  else {
    this.comboBox1.Items.Add(item);
  }
}


Hope this helps. Cheers!