C#自定义WPF中Slider的Autotooltip模板

/// 

/// A Slider which provides a way to modify the 
/// auto tooltip text by using a format string.
/// 
public class FormattedSlider : Slider
{
    private ToolTip _autoToolTip;
    private string _autoToolTipFormat;

    /// 

    /// Gets/sets a format string used to modify the auto tooltip\'s content.
    /// Note: This format string must contain exactly one placeholder value,
    /// which is used to hold the tooltip\'s original content.
    /// 
    public string AutoToolTipFormat
    {
        get { return _autoToolTipFormat; }
        set { _autoToolTipFormat = value; }
    }

    protected override void OnThumbDragStarted(DragStartedEventArgs e)
    {
        base.OnThumbDragStarted(e);
        this.FormatAutoToolTipContent();
    }

    protected override void OnThumbDragDelta(DragDeltaEventArgs e)
    {
        base.OnThumbDragDelta(e);
        this.FormatAutoToolTipContent();
    }

    private void FormatAutoToolTipContent()
    {
        if (!string.IsNullOrEmpty(this.AutoToolTipFormat))
        {
            this.AutoToolTip.Content = string.Format(
                this.AutoToolTipFormat, 
                this.AutoToolTip.Content);
        }
    }

    private ToolTip AutoToolTip
    {
        get
        {
            if (_autoToolTip == null)
            {
                FieldInfo field = typeof(Slider).GetField(
                    \"_autoToolTip\",
                    BindingFlags.NonPublic | BindingFlags.Instance);

                _autoToolTip = field.GetValue(this) as ToolTip;
            }

            return _autoToolTip;
        }
    }    
}

private ToolTip AutoToolTip
{
    get
    {
        if (_autoToolTip == null)
        {
            FieldInfo field = typeof(Slider).GetField(
                \"_autoToolTip\",
                BindingFlags.NonPublic | BindingFlags.Instance);

            _autoToolTip = field.GetValue(this) as ToolTip;
        }

        return _autoToolTip;
    }
}