How do I create a dashed border with rounded corners in WPF?

Question

The Rectangle element has StrokeDashArray which allows it to be drawn with dashes, but it doesn\'t support rounded corners. The Border

Answer 1

You are mistaken that Rectangle does not support this:

<Rectangle StrokeDashArray="0.5 1.0 0.3" Stroke="Black" StrokeThickness="2" RadiusX="10" RadiusY="10"/>

Answer 2

WPF Border control does not support dashed lines. If you want to apply a dotted/dashed border for a control, you can simply decorate the control with an adorner.

Here is the sample adorner class. This is a generic adorner for any UIelement.

class DottedLineAdorner : Adorner
{
    public UIElement AdornedElement { get; set; }

    public DottedLineAdorner(UIElement adornedElement) : base(adornedElement)
    {
        AdornedElement = adornedElement;
    }

    protected override void OnRender(DrawingContext drawingContext)
    {
        Size eltSize = (AdornedElement as FrameworkElement).DesiredSize;
        Pen pen = new Pen(Brushes.Blue, 2) { DashStyle = DashStyles.DashDot };
        drawingContext.DrawRoundedRectangle(null, pen, new Rect(0, 0, eltSize.Width, eltSize.Height), 10, 10);
    }
}

I have a simple textblock in my xaml and it is contained in a grid named 'LayoutGrid'.

Now, the border can be applied in the code behind

    private void Window_Loaded(object sender, RoutedEventArgs e)
    {
        AdornerLayer.GetAdornerLayer(LayoutGrid).Add(new DottedLineAdorner(textblock));
    }