1. Tutorial 9 - Car Payment Calculator Application Introducing the while Repetition Statement
Outline
9.1 Test-Driving the Car Payment Calculator Application 9.2 while Repetition Statement 9.3 Constructing the Car Payment Calculator Application 9.4 Wrap-Up

2. In this tutorial, you will learn to:
Objective
In this tutorial, you will learn to:
Use the while repetition statement to execute statements in a program repeatedly.
Use counter-controlled repetition.
Display information in ListBoxes.

3. 9.1 Test-Driving the Car Payment Calculator Application

4. 9.1 Test-Driving the Car Payment Calculator Application
Figure 9.1　Car Payment Calculator application before data has been entered.
ListBox control

5. 9.1 Test-Driving the Car Payment Calculator Application
Figure 9.2　Car Payment Calculator application after data has been entered.
Input data
Click Calculate Button

6. 9.1 Test-Driving the Car Payment Calculator Application
Figure 9.3　Car Payment Calculator application displaying calculation results.
Results displayed in tabular format

7. 9.2 while Repetition Statement
Loop-continuation condition
While loop-continuation condition remains true, loop statement executes its body repeatedly
When loop-continuation condition becomes false, loop terminates
Code example:
int intProduct = 3; while ( intProduct <= 50 ) { intProduct *= 3; }

8. 9.2 while Repetition Statement
Figure 9.4　while repetition statement UML activity diagram. [
intProduct
<= 50 ]
>
triple product value
merge
decision
Corresponding C#
statement: *= 3;

9. 9.3 Constructing the Car Payment Calculator Application

10. 9.3 Constructing the Car Payment Calculator Application

11. 9.3 Constructing the Car Payment Calculator Application
Figure 9.6　Car Payment Calculator application’s Form in design mode.

12. 9.3 Constructing the Car Payment Calculator Application
Figure 9.7　ListBox added to Car Payment Calculator application’s Form.
ListBox’s control name displayed in design view
ListBox control
Change the Name property

13. 9.3 Constructing the Car Payment Calculator Application
Figure 9.8　Rearranging and commenting the ListBox control declaration.

14. 9.3 Constructing the Car Payment Calculator Application
Adding code to the event handler
Clearing the ListBox
Call method Clear on property Items
Items property returns an object containing items in ListBox

15. 9.3 Constructing the Car Payment Calculator Application
Figure 9.9　Clearing the contents of a ListBox.

16. 9.3 Constructing the Car Payment Calculator Application
Adding a header to the ListBox
Call method Add
Escape sequences \t

17. 9.3 Constructing the Car Payment Calculator Application
Figure 9.10　Adding a header to a ListBox.

18. 9.3 Constructing the Car Payment Calculator Application

19. 9.3 Constructing the Car Payment Calculator Application
Figure 9.12　Variables for the Car Payment Calculator application.
Variables to store the length of the loan
Variables to store user input
Variables to store calculation results
• Variable declarations

20. 9.3 Constructing the Car Payment Calculator Application
Figure 9.13　Retrieving input in the Car Payment Calculator application.
Retrieving input
Use Int32.Parse and Double.Parse methods
Divide interest rate by 100

21. 9.3 Constructing the Car Payment Calculator Application
Calculating values used in the calculation
Subtract down payment from price
Monthly interest rate is interest divided by 12

22. 9.3 Constructing the Car Payment Calculator Application
Figure 9.14　Determining amount borrowed and monthly interest rate.

23. 9.3 Constructing the Car Payment Calculator Application
Setting the loop-continuation condition
Counter-controlled repetition
Uses a counter variable
Also called definite repetition

24. 9.3 Constructing the Car Payment Calculator Application
Figure 9.15　Loop-continuation condition.

25. 9.3 Constructing the Car Payment Calculator Application
Figure 9.16　Converting the loan duration from years to months.
Add the length of the loan in months

26. 9.3 Constructing the Car Payment Calculator Application
Calculate monthly payment amount
Use given formula
Type Decimal stores monetary values
Use the Convert.ToDecimal method

27. 9.3 Constructing the Car Payment Calculator Application
Figure 9.17　Calculating the monthly payment

28. 9.3 Constructing the Car Payment Calculator Application
Displaying the result
Use method Add
Use method String.Format to display values in currency format

29. 9.3 Constructing the Car Payment Calculator Application
Figure 9.18　Displaying the number of months and the amount of each monthly payment.

30. 9.3 Constructing the Car Payment Calculator Application
Increment the counter
Add one to the counter
Will terminate the loop when value becomes 6

31. 9.3 Constructing the Car Payment Calculator Application
Figure 9.19　Incrementing the counter.

32. CarPayment-Calculator.cs (1 of 6)

33. CarPayment-Calculator.cs (2 of 6)
Declaration for a ListBox control

34. CarPayment-Calculator.cs (3 of 6)

35. CarPayment-Calculator.cs (4 of 6)
Using the Clear method of property Items of a ListBox
Using the Add method of property Items of a ListBox

36. CarPayment-Calculator.cs (5 of 6)
Using a while repetition statement
Using the Math.Pow method
Incrementing the counter

37. CarPayment-Calculator.cs (6 of 6)