object drop in canvas on button click event

you’ve already got a dynamic grid setup with buttons and DesignerCanvas controls.
Now you want to add a Rectangle shape onto the corresponding canvas when a button is clicked.

Let’s go step-by-step to make this clear and working.

Goal

When you click Button 1, a Rectangle should appear on DesignerCanvas “Rung1”.
When you click Button 2, a Rectangle should appear on DesignerCanvas “Rung2”.

Step 1: Modify Button_Click Event

You already wire up:

button.Click += Button_Click;

Now implement it like this

private void Button_Click(object sender, RoutedEventArgs e)
{
    Button btn = sender as Button;
    string rungId = btn.Tag.ToString();

    // Find the matching DesignerCanvas by name
    var canvasBorder = MainStK.Children
        .OfType()
        .FirstOrDefault(b => (b.Child is DesignerCanvas dc) && dc.Name == "Rung" + rungId);

    if (canvasBorder != null && canvasBorder.Child is DesignerCanvas designerCanvas)
    {
        AddRectangleToCanvas(designerCanvas);
    }
}

Step 2: Create Helper Method to Add Rectangle

private void AddRectangleToCanvas(Canvas designerCanvas)
{
    Rectangle rect = new Rectangle
    {
        Width = 100,
        Height = 50,
        Fill = Brushes.LightBlue,
        Stroke = Brushes.DarkBlue,
        StrokeThickness = 2
    };

    // Set random or fixed position
    Canvas.SetLeft(rect, 50);
    Canvas.SetTop(rect, 30);

    designerCanvas.Children.Add(rect);
}

If your DesignerCanvas is a subclass of Canvas (which is typical in WPF drag-drop designers),
this will work perfectly — the rectangle will appear inside that canvas.

Step 3: Confirm DesignerCanvas Inherits from Canvas

Make sure your DesignerCanvas is declared like:

public class DesignerCanvas : Canvas
{
    // your logic (drag-drop, etc.)
}

If it’s derived from something else (like Grid or Border),
just replace the call to Canvas.SetLeft() and Canvas.SetTop()
with layout logic suitable for that panel.

Full Working Snippet (Simplified)

Here’s a clean version for clarity:

private void Button_Click(object sender, RoutedEventArgs e)
{
    Button btn = sender as Button;
    string rungId = btn.Tag.ToString();

    var canvasBorder = MainStK.Children
        .OfType()
        .FirstOrDefault(b => (b.Child is DesignerCanvas dc) && dc.Name == "Rung" + rungId);

    if (canvasBorder != null && canvasBorder.Child is DesignerCanvas designerCanvas)
    {
        AddRectangleToCanvas(designerCanvas);
    }
}

private void AddRectangleToCanvas(Canvas designerCanvas)
{
    Rectangle rect = new Rectangle
    {
        Width = 100,
        Height = 50,
        Fill = Brushes.LightBlue,
        Stroke = Brushes.DarkBlue,
        StrokeThickness = 2
    };

    Canvas.SetLeft(rect, 50);
    Canvas.SetTop(rect, 30);

    designerCanvas.Children.Add(rect);
}

Optional Enhancement

You can make rectangle placement dynamic — for example:

• Random positions

• Positions based on previous shapes count

• Allow dragging (if your DesignerCanvas supports it)

Example:

Canvas.SetLeft(rect, designerCanvas.Children.Count * 120);