[CODE]
List<dynamic> lista = Assembly.GetExecutingAssembly().GetTypes().Where(t => t.BaseType==typeof(UserControl))
               .Select(p => Activator.CreateInstance(p))
                   .OfType<dynamic>()
                   .ToList();
            lista[0].Testo = "ciao";
            this.panel1.Controls.Add(lista[0]);
[/CODE]