title: Refresh data in ListBox after add new one
body: <p>Good morning,</p>
  
  <p>I want to refresh data with Binding in listbox after then I add new one.
  I'm using MVVM design patter, so my ViewModel has property AllGroups and every group have property TotalCount and Name.
  Property AllGroups is ObservableCollection.</p>
  
  <p>In listbox I show name of group and TotalCount.
  TotalCount has just getter realized by </p>
  
  <pre><code>public int TotalCount
  {
    get
    {
      return Items.Count;
    }
  }
  </code></pre>
  
  <p>and TotalCount isn't column.</p>
  
  <p>I have group "All" with 2 items (TotalCount=2), but when I add new item to group and show list of groups I see "All" and TotalCount=2 but when I start app again I show "All" and "3".</p>
  
  <p>So, how can I refresh data manually? Thank for help. :)</p>