title: Raise event on WPF DataGrid upon datasource change
body: <p>I am working on an WPF MVVM application. I want some kind of event should fires when the collection that is bind to my datagrid changes.</p>
  
  <p>Ex:- My datagrid item source is ObservableCollection UserList</p>
  
  <p>I want when i clear UserList collection, some event fires on datagrid to notify itself. I've tried this event DataContextChanged of datagrid, but it didn't help.</p>
  
  <p>Please guide</p>
  
  <p>Thanks</p>