3. 3 private void equalsButton_Click( object sender, RoutedEventArgs e) { calculateResult(); }

4. 4

5. 5

6. 6 private void firstNumberTextBox_TextChanged( object sender,TextChangedEventArgs e) { calculateResult(); }

7. 7 string oldFirstNumber = ""; private void firstNumberTextBox_TextChanged( object sender, TextChangedEventArgs e) { if (firstNumberTextBox.Text == oldFirstNumber) return; oldFirstNumber = firstNumberTextBox.Text; calculateResult(); }

8. 8

9. 9

10. 10

11. 11

12. 12

13. 13 public class AdderClass { private int topValue; public int TopValue { get { return topValue; } set { topValue = value; } } // repeat for bottomValue public int AnswerValue { get { return topValue + bottomValue;} } }

14. 14

15. 15 public interface INotifyPropertyChanged { // Summary: // Occurs when a property value changes. event PropertyChangedEventHandler PropertyChanged; }

16. 16 PropertyChanged(this, new PropertyChangedEventArgs("AnswerValue"));

17. 17 public int AnswerValue { get { return topValue + bottomValue; } }

18. 18

19. 19 xmlns:local="clr-namespace:AddingMachine"

20. 20

21. 21

22. 22

23. 23

24. 24

25. 25

26. 26