static void Main(string[] args)
{
var o = new ObjectStructure();
o.Add(new ConcreteElementA());
o.Add(new ConcreteElementB());
o.Add(new ConcreteElementB());
o.Delete(new ConcreteElementB());
var v1 = new ConcreteVisitor1();
var v2 = new ConcreteVisitor2();
o.Accept(v1);
o.Accept(v2);
Console.ReadKey();
}