private void btnUndo_Click(object sender, RoutedEventArgs e) { DrawArea.Undo(); if (DrawArea.CanRedo == true) { btnRedo.IsEnabled = true; } else if (DrawArea.CanRedo == false) { btnRedo.IsEnabled = false; } if (DrawArea.CanUndo == true) { btnUndo.IsEnabled = true; } else if (DrawArea.CanUndo == false) { btnUndo.IsEnabled = false; } }