public abstract bool Contains(DrawingElement d);
public abstract void Remove(DrawingElement d);
public override void Remove(DrawingElement d) { _elements.Remove(d); }
public abstract void Add(DrawingElement d);
public override bool Contains(DrawingElement d) { if (_elements.Contains(d)) return true; return false; }
public override void Add(DrawingElement d) { _elements.Add(d); }
public override void Remove(DrawingElement c) { Console.WriteLine( "Cannot remove from a PrimitiveElement"); }
public override bool Contains(DrawingElement d) { return false; }
public override void Add(DrawingElement c) { Console.WriteLine( "Cannot add to a PrimitiveElement"); }