WPF /线程：控件上的Dispatcher static vs Dispatcher？

I'm a bit confused in terms of the dispatcher. Say I'm on a background thread doing some kind of long operation. I'd like to update the ui thread I understand I do this through the dispatcher. My question is, do i call the dispatcher statically like: Dispatcher.BeginInvoke(mywork) ... Or on the control i want to update: mytextbox.Dispatcher.BeginInvoke(mywork)I'm a bit confused in terms of the dispatcher.