Generally, you shouldn't need to refresh the user interface of our WPF or Silverlight™ controls manually, as they would automatically refresh themselves whenever the data changes, provided that the bound collections implement INotifyCollectionChange (or IBindingListView), request already fulfilled by ObservableCollection<T> (or BindingList<T>), and that collection item types properly implement INotifyPropertyChanged.
To understand how to implement the INotifyPropertyChanged interface, please read this MSDN article.