public void Remove(IFIleSystemElement element)
 {
     children.Remove(element);
 }
 public void Remove(IFIleSystemElement element)
 {
     Console.WriteLine("Cannot remove");
 }
 public void Add(IFIleSystemElement element)
 {
     children.Add(element);
 }
 public void Add(IFIleSystemElement element)
 {
     Console.WriteLine("Cannot add");
 }