title: How to fire CollectionChanged event in code for INotifyCollectionChanged/ObservableCollection?
body: <p>I define an ObservableCollection in ViewModel like:</p>
  
  <pre><code>//private ObservableCollection&lt;MyObject&gt; _myList;
  public ObservableCollection&lt;MyObject&gt; MyList {get;set;}
  </code></pre>
  
  <p>Then I try to bind it to SelectedItems for ListBox with behavior like:</p>
  
  <pre><code>&lt;i:Interaction.Behaviors&gt;
    &lt;My:ListBoxSelectedItemsBehavior SelectedItems="{Binding MyList, Mode=TwoWay}" /&gt;
  &lt;/i:Interaction.Behaviors&gt;
  </code></pre>
  
  <p>Then enable multiple selection for this listbox. It is fine when selceted more than one item by user interaction with mouse.</p>
  
  <p>Question: initially, there are selected item data stored in database, when data is retrieved from database, I need to fire CollectionChanged and let those selectedItem display as selected in UI. Even I did RaisePropertyChanged in ViewModel for MyList when data is loaded, UI still not display those items as selected.  After debug the app, I found even MyList is loaded, CollectionChanged fired for Mylist in ViewModel, but CollectionChanged event not fired for the binding item SelectedItems in ListBoxSelectedItemsBehavior although it is bound to MyList. </p>
  
  <p>How to resolve this problem?</p>