System.NullReferenceException occurred
  Message=Object reference not set to an instance of an object.
  StackTrace:
       at Infragistics.DataManager`1.OnDataSourceCollectionChanged(NotifyCollectionChangedEventArgs e)
       at Infragistics.DataManagerBase.DataSource_CollectionChanged(Object sender, NotifyCollectionChangedEventArgs e)
       at System.Collections.Specialized.NotifyCollectionChangedEventHandler.Invoke(Object sender, NotifyCollectionChangedEventArgs e)
       at System.Windows.Data.CollectionView.OnCollectionChanged(NotifyCollectionChangedEventArgs args)
       at System.Windows.Data.ListCollectionView.RefreshOverride()
       at System.Windows.Data.CollectionView.Refresh()
       at SecurityApp.SecCaps.btnSitesMoveToSelected_Click(Object sender, RoutedEventArgs e)
  InnerException: