If you want, for example, to show in a text box loop iterations in a real time, then you have to use something like:

Dispatcher.CurrentDispatcher.Invoke(DispatcherPriority.Background, new Action(
  () =>
	  DisplayCount = i.ToString();
	  OnPropertyChanged(() => this.DisplayCount);

Where DiplayCount is property to which TextBox is binded. Here I explained how to use INotifyPropertyChanged, and from here you can download example.