private void SetupVisual()
{
var hostVisual = ElementCompositionPreview.GetElementVisual(element: ShadowHost);
var compositor = hostVisual.Compositor;
// Create a drop shadow
DropShadow dropShadow = compositor.CreateDropShadow();
dropShadow.Color = Color.FromArgb(255, 22, 33, 44);
dropShadow.BlurRadius = 15.0f;
dropShadow.Offset = new Vector3(12.5f, 2.5f, 0.0f);
// Associate the shape of the shadow with the shape of the target element
dropShadow.Mask = CircleImage.GetAlphaMask();
// Create a Visual to hold the shadow
SpriteVisual shadowVisual = compositor.CreateSpriteVisual();
shadowVisual.Shadow = dropShadow;
// Add the shadow as a child of the host (Ellipse) in the visual tree
ElementCompositionPreview.SetElementChildVisual(element: ShadowHost,
visual: shadowVisual);
// Ensure the size of shadow host and shadow visual always stay in sync
ExpressionAnimation bindSizeAnimation = compositor.CreateExpressionAnimation(expression: "hostVisual.Size");
bindSizeAnimation.SetReferenceParameter(key: "hostVisual", compositionObject: hostVisual);
shadowVisual.StartAnimation(propertyName: nameof(shadowVisual.Size),
animation: bindSizeAnimation);
}