title: MVVMLight Multiple Listbox Selection
body: <p>I have an ItemsContol bound to a Country model - which look like this.</p>
  
  <hr>
  
  <p>Country<br>
  --int Id<br>
  --string Name<br>
  --List Counties  </p>
  
  <hr>
  
  <p>In the DataTemplate of the ItemsControl there's a Listbox - which is bound to the Counties property.</p>
  
  <p>So what I want is only one item in any of the listboxes be selected at any one time.</p>
  
  <p>For example:
  I have an item selected in the first listbox and I click an item in the second listbox, then the first listbox shouldn't have any selected items.</p>
  
  <p>Any ideas ??</p>