title: Events for adding/removing items in a listbox c#.NET
body: <p>I have a listbox control that has <code>item</code>s dynamically added to and manually removed from (due to 'remove item' button). When the number of items is changed, I would like to update other parts of the user interface - namely a caption that says 'You must choose some files.' and an item count caption.</p>
  
  <p>How can an event handler or effectively an event handler be added to fire when the number of items is changed - e.g. an <code>ItemAdded</code> or <code>ItemRemoved</code> or <code>ItemsChanged</code></p>
  
  <p>Note: This is nothing to do with the user selecting items in the listbox.</p>
  
  <p>Thanks very much!</p>