title: Silverlight - Block the screen while the ListBox is rendering using BusyIndicator
body: <p>I have a ListBox which is wrapped by a BusyIndicator. The ListBox is quite heavy sometimes it could take 4 or 5 seconds to render.</p>
  
  <p>I wonder what is the best way to block the UI using the BusyIndicator while the ListBox is rendering?</p>
  
  <p>Edit: Sorry I didn't make my question very clear... Please be aware of that the ItemsSource of the ListBox is bound to an ObservabaleCollection in the viewmodel. This colletion is populated fast. The thing I guess that really slows everything down is the UI rendering as the ListBox contains customised ListBoxItems which are quite complex.</p>
  
  <p>Also the ListBox's ItemsPanel is a WrapPanel. It's not like the default VirtualisingStackPanel, so I guess this could be a ListBox performance issue?</p>