In addition to the above four questions, I have another question: What I want is that no matter if I scroll the mouse wheel at any point of the imageNode or overlayNode to zoom in, the maximum zoom will be the effect of the following screenshot. How to achieve this? What changes should be made to this code?
        private void diagram_MouseWheel(object sender, MouseWheelEventArgs e)
        {
            var imageBounds = imageNode.Bounds;
            var zoomRect = diagram.Viewport;
            var zoomStep = 10;

            if (e.Delta < 0)
            {
                zoomRect = new Rect
                (
                    Math.Max(imageBounds.X, zoomRect.X - zoomStep / 2),
                    Math.Max(imageBounds.Y, zoomRect.Y - zoomStep / 2),
                    Math.Min(imageBounds.Width, zoomRect.Width + zoomStep),
                    Math.Min(imageBounds.Height, zoomRect.Height + zoomStep)
                );
            }
            else
            {
                zoomRect = new Rect
                (
                    Math.Min(overlayNode.Bounds.X, zoomRect.X + zoomStep / 2),
                    Math.Min(overlayNode.Bounds.Y, zoomRect.Y + zoomStep / 2),
                    Math.Max(overlayNode.Bounds.Width, zoomRect.Width - zoomStep),
                    Math.Max(overlayNode.Bounds.Height, zoomRect.Height - zoomStep)
                );
            }

            diagram.ZoomToRect(zoomRect, true);

            // stop the scrollviewer from scrolling
            e.Handled = true;

        }

Hi,

As already suggested, the code provided above lets you limit both your zooming in and zooming out operations to whatever values you have in your requirements. Just replace the imageBounds variable with the bounding rectangle of your outer limits and the redRect variable with the bounding rectangle of your inner limits.

If that approach doesn't work for you, you can use the diagram ZoomFactor property to limit the level of magnification.

Regards,
Lyubo
MindFusion

Thanks a lot, Luybo.
It's strange, zoom in to the maximum extent, if you still use the wheel to scroll, it will move the imageNode, I don't want this. When I want to zoom in to the maximum, if I still use the wheel to scroll, the imageNode cannot move, which is equivalent to not responding to the wheel message. How can I solve it?

Thank you, Lyubo. I have carefully read the example you gave me. Many of the contents are what I want and I have learned a lot. But the example does not contain the content of my problem above. Please guide me to complete this content: When I zoom in to the maximum, if I still use the mouse wheel to zoom in, the ShapeNode should not move, which is equivalent to not responding to the wheel message. How can I achieve it?

I tried the following method and it still doesn't work. When zooming in is no longer possible, if the scroll wheel is still zoomed in, the ShapeNode still moves. I would like to ask how to prohibit this ShapeNode movement.

        private void diagram_PreviewMouseWheel(object sender, MouseWheelEventArgs e)
        {
            var imageBounds = imageNode.Bounds;
            var zoomRect = diagram.Viewport;
            var zoomStep = 10;

            if (e.Delta < 0)
            {
                zoomRect = new Rect
                (
                    Math.Max(imageBounds.X, zoomRect.X - zoomStep / 2),
                    Math.Max(imageBounds.Y, zoomRect.Y - zoomStep / 2),
                    Math.Min(imageBounds.Width, zoomRect.Width + zoomStep),
                    Math.Min(imageBounds.Height, zoomRect.Height + zoomStep)
                );
            }
            else
            {
                zoomRect = new Rect
                (
                    Math.Min(overlayNode.Bounds.X, zoomRect.X + zoomStep / 2),
                    Math.Min(overlayNode.Bounds.Y, zoomRect.Y + zoomStep / 2),
                    Math.Max(10, zoomRect.Width - zoomStep),
                    Math.Max(10, zoomRect.Height - zoomStep)
                );
            }

            if (!zoomRect.Contains(diagram.Factory.CreateShapeNode(overlayNode.Bounds.X, overlayNode.Bounds.Y, 10, 10).Bounds))
            {
                diagram.ZoomToRect(zoomRect, true);
            }

            // stop the scrollviewer from scrolling
            e.Handled = true;
        }

Hey, Lyubo.

I don't quite understand your answer above. Is there any sample code for my reference?
I desperately need it.

Added:

Hey, Lyubo. There is no need to tell me this answer, because you told me before, please give me a detailed answer to my question, because every question I think about how to ask you seriously, and hope you answer my questions one by one Every question. After completing this project or at the end of this month, I will purchase the right to use MindFusion. I hope you can guide me. Can you take a closer look at my problem?