private void userDo_StackPushed(object sender, StackEventAgrs e)
{
if (_userDo.Count == 1)
{
btnUndo.Enabled = true;
}
}
private void userDo_StackPopped(object sender, StackEventAgrs e)
{
if (_userDo.Count == 0)
{
btnUndo.Enabled = false;
}
}
