Drag the edge or diagonal of overlayNode to change the size of overlayNode. How to achieve this?

Thank you very much for your answer, Lyubo.
Do you say "please make sure the ShapeNode.Locked property is set to false" refers to setting imageNode.Locked and overlayNode.Locked to false? Also, I do n’t quite understand what you said about “The visual effect of covering the background node in NodeModfied handler is invalid to update the transparent layer”. Is there any sample code?
cs:
        private void ImageManipulation(string path)
{
var myImage = new BitmapImage(new Uri(path, UriKind.Relative));

var imageWidthPx = myImage.PixelWidth * GetScreenDpi() / myImage.DpiX;
var imageHeightPx = myImage.PixelHeight * GetScreenDpi() / myImage.DpiY;
var imageWidth = GraphicsUnit.Pixel.Convert(imageWidthPx, diagram.MeasureUnit);
var imageHeight = GraphicsUnit.Pixel.Convert(imageHeightPx, diagram.MeasureUnit);

imageNode = diagram.Factory.CreateShapeNode(0, 0, imageWidth, imageHeight);
imageNode.Image = myImage;
imageNode.Shape = Shapes.Rectangle;
imageNode.CustomDraw = CustomDraw.Additional;
imageNode.ImageAlign = ImageAlign.Fit;
//overlayNode = diagram.Factory.CreateShapeNode(0, 0, 150, 150);
var overlayNodeWidth = 100;
var overlayNodeHeight = 100;

overlayNode = diagram.Factory.CreateShapeNode(imageNode.Bounds.Right - overlayNodeWidth,
imageNode.Bounds.Bottom - overlayNodeHeight, overlayNodeWidth, overlayNodeHeight);
overlayNode.Shape = Shapes.Rectangle;
overlayNode.Brush = Brushes.Transparent;
overlayNode.StrokeThickness = 0.8;
overlayNode.Stroke = new SolidColorBrush(Color.FromArgb(120, 12, 236, 13));
overlayNode.Locked = true;
overlayNode.AttachTo(imageNode, AttachToNode.BottomRight);
}

Thank you so much, Lyubo. I know that my code is definitely wrong, please guide me to correct it and
how to add NodeModifed event handler for overlayNode.