BackgroundWorker - Cross-thread operation not valid

Question

I have a winform application (one form), on this form there is a RichTextBox. In the constructor of this form I create an instance of the class MyClass. In the

Answer 1

Using BackgroundWorker doesn't exempt you of the normal threading rules - such as that only the UI thread can access UI components.

If you want to update the UI from a BackgroundWorker other than using the progress/completion events (which are raised on the UI thread) you need to use Control.Invoke / Control.BeginInvoke just as you would in other situations. For example:

if (....)
{
    Action action = () => richtextBox.Text.Add("MyText");
    richtextBox.Invoke(action); // Or use BeginInvoke
}