@Command 
	//@NotifyChange("selectedTodo") //use postNotifyChange() to notify dynamically
	public void completeTodo(@BindingParam("todo") Todo todo){
		//save data
		todo = todoListService.updateTodo(todo);
		if(todo.equals(selectedTodo)){
			selectedTodo = todo;
			//for the case that notification is decided dynamically
			//you can use BindUtils.postNotifyChange to notify a value changed
			BindUtils.postNotifyChange(null, null, this, "selectedTodo");
		}
	}