public Memento2 Deposit(int amount)
{
balance += amount;
var m = new Memento2(balance);
changes.Add(m);
++current;
return(m);
}
// add a restore state from memento
public Memento2 Restore(Memento2 m)
{
// make sure there is something to undo.
if (m != null)
{
balance = m.Balance;
changes.Add(m);
return(m);
}
return(null);
}