Compartiendo elementos en posiciones dependientes del contenedor

Elements.cs

public interface IElement
{
  IEnumerable<ChildElement> Children { get; }
}

public class ChildElement 
{
  public readonly IElement Value;
  public readonly Point Point;
  
  public ChildElement(int x, int y, IElement value)
  {
    Point = new Point(x, y);
    Value = value;
  }
}

public class Container : IElement
{
  private readonly ISet<ChildElement> children = new HashSet<ChildElement>();
  
  public Container Add(int x, int y, IElement child)
  {
    children.Add(new ChildElement(x, y, child));
    return this;
  }
  
  public IEnumerable<ChildElement> Children
  {
    get { return children.AsEnumerable();
  }
}

var shared = new FormElement();

var page1 = new Container()
  .Add(3, 1, new CircleElement(radius: 6))
  .Add(25, 25, shared);
  .Add(10, 50, new Container()
    .Add(1, 1, new TextElement(text: "Sample Text Element"))
    .Add(5, 5, new BoxElement(width: 100, height: 25)));
    
var page2 = new Container()
  .Add(4, 4, new TitleElement(text: "The Title of this Page"))
  .Add(10, 10, shared);