WPF控件中的取消订阅事件

        EventHandler ReCalculateWidthsHandler;
        public RangeSlider()
        {
            ReCalculateWidthsHandler = OnReCalculateWidths;
            DependencyPropertyDescriptor.FromProperty(ActualWidthProperty, typeof(RangeSlider)).
                AddValueChanged(this, ReCalculateWidthsHandler);
        }