private void revertStackFrames()
{
Debug.Assert(stackULEs != null);
if (savedTopOfStack != null)
savedTopOfStack.DoRevert();
while (stackULEs.Count > 0)
{
StackULE ule = (StackULE)stackULEs.Pop();
ule.Undo();
}
Debug.Assert(savedTopOfStack == topOfStack);
}