如何允许用户在WPF中向UI控件添加注释？

    <ToolTipService.ToolTip>
        Click this button to perform an action.
    </ToolTipService.ToolTip>
</Button>

   <Button.Triggers>
       <EventTrigger RoutedEvent="Button.Click">
           <BeginStoryboard>
               <Storyboard>
                   <ObjectAnimationUsingKeyFrames Storyboard.TargetName="myPopup" Storyboard.TargetProperty="IsOpen">
                        <DiscreteObjectKeyFrame KeyTime="0:0:0">
                            <DiscreteObjectKeyFrame.Value>
                                <sys:Boolean>True</sys:Boolean>
                            </DiscreteObjectKeyFrame.Value>
                        </DiscreteObjectKeyFrame>
                    </ObjectAnimationUsingKeyFrames>
                </Storyboard>
            </BeginStoryboard>
        </EventTrigger>
    </Button.Triggers>
</Button>

<Popup x:Name="myPopup" PlacementTarget="{Binding ElementName=myButton}" Placement="Bottom">
   <Border Background="White" BorderBrush="Black" BorderThickness="1" CornerRadius="5" Padding="5">
        <TextBlock Text="This is an annotation."/>
    </Border>
</Popup>

public class AnnotationAdorner : Adorner
{
    private readonly UIElement _child;

    public AnnotationAdorner(UIElement adornedElement, UIElement child)
        : base(adornedElement)
    {
        _child = child;
    }

    protected override Visual GetVisualChild(int index)
    {
        return _child;
    }

    protected override int VisualChildrenCount
    {
        get { return 1; }
    }

    protected override Size MeasureOverride(Size constraint)
    {
        _child.Measure(constraint);
        return _child.DesiredSize;
    }

    protected override Size ArrangeOverride(Size finalSize)
    {
        _child.Arrange(new Rect(finalSize));
        return finalSize;
    }
}

var annotation = new TextBlock { Text = "This is an annotation.", Background = Brushes.White, BorderBrush = Brushes.Black, BorderThickness = new Thickness(1), CornerRadius = new CornerRadius(5), Padding = new Thickness(5) };
var adorner = new AnnotationAdorner(myButton, annotation);
AdornerLayer.GetAdornerLayer(myButton).Add(adorner);