CustomSlider WPF

/*
     <vw:CustomSlider Minimum="1"
                    AutoToolTipPlacement="TopLeft"
                    AutoToolTipContent="{Binding DateFiltersToolTip}"
                    Maximum="{Binding DateFilters.Count}"
                    TickFrequency="1"
                    TickPlacement="BottomRight"
                    HorizontalAlignment="Left"
                    SmallChange="1" LargeChange="5"
                                Width="200"
                                Visibility="Collapsed"
                        ValueChanged="Slider_ValueChanged"/>
     */
    public class CustomSlider : Slider
    {
        public object AutoToolTipContent
        {
            get { return GetValue(AutoToolTipContentProperty); }
            set { SetValue(AutoToolTipContentProperty, value); }
        }

        // Using a DependencyProperty as the backing store for AutoToolTip.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty AutoToolTipContentProperty =
            DependencyProperty.Register("AutoToolTipContent", typeof(object), typeof(CustomSlider), new PropertyMetadata(null));


        protected override void OnThumbDragStarted(System.Windows.Controls.Primitives.DragStartedEventArgs e)
        {
            base.OnThumbDragStarted(e);
            AutoToolTipObj.Content = this.AutoToolTipContent;
        }

        protected override void OnThumbDragDelta(System.Windows.Controls.Primitives.DragDeltaEventArgs e)
        {
            base.OnThumbDragDelta(e);
            AutoToolTipObj.Content = this.AutoToolTipContent;
        }

        ToolTip autoToolTipObj;
        public ToolTip AutoToolTipObj
        {
            get
            {
                if (autoToolTipObj == null)
                {
                    var fld = typeof(Slider).GetField("_autoToolTip", BindingFlags.NonPublic | BindingFlags.Instance);
                    if (fld != null)
                        autoToolTipObj = fld.GetValue(this) as ToolTip;
                }
                return autoToolTipObj;
            }
        }
    }