title: Selection Changed Event using MVVM
body: <p>I have a <strong>listbox</strong> that contains a list of persons.
  When the user clicks on an item the viewModel should set the currentPerson object to the Object the user has clicked on.</p>
  
  <p>I have to use a ViewModel for this, so <strong>no code inside the MainWindow.xaml.xs</strong>. Any Ideas how to solve this?</p>