Dispatcher.Invoke doesn't change value of Label

Dispatcher.Invoke doesn't change value of Label

In the thread I want to change value of Label
I found out that I have to use Dispatcher.Invoke.
Tried this code:
Me.Dispatcher.Invoke(DispatcherPriority.Background, (Function()
Me.Label2.Content = "Scanning done."))
but it doesn't change the value.
What am I doing wrong?