public override void Render(IDrawingContext drawingContext)
{
drawingContext.FillRoundedRectangle(Background, VisualBounds, new CornerRadius(CornerRadius));
drawingContext.DrawRoundedRectangle(new Pen(BorderBrush, BorderThickness), VisualBounds, new CornerRadius(CornerRadius));
base.Render(drawingContext);
}