10.13 ( Arithmetic Calculator App) Write an app that allows the user to enter a

Question

10.13 ( Arithmetic Calculator App) Write an app that allows the user to enter a series of numbers and manipulate them. The app should provide users with the option of adding or multiplying the numbers. Users should enter each number in a TextBox. After entering the number, the user clicks a Button, and the number is inserted in a ListBox. The GUI should behave as in Fig. 10.20.

a) Copying the template to your working directory. Copy the directory C: Examples ch10 Exercises ArithmeticCalculator to your C: SimplyVB2010 directory.

b) Opening the apps template file. Double click ArithmeticCalculator. sln in the ArithmeticCalculator directory to open the app.

c) Adding a ListBox to display the entered numbers. Add a ListBox. Place and size it as in Fig. 10.20.

d) Creating an event handler for the Enter Button. Create the Click event handler for the Enter Button. If the result of a previous calculation is displayed, this event han-dler should clear the result, clear the ListBox and disable the addition and multipli-cation Buttons. It should then insert the current number in the Operands list: ListBox. When the ListBox contains at least two numbers, the event handler should then enable the addition and multiplication Buttons.

e) Summing the values in the ListBox. Define the Click event handler for the Add Button. This event handler should compute the sum of all the values in the Oper-ands list: ListBox and display the result in resultLabel.

f) Multiplying the values in the ListBox. Define the Click event handler for the Mul-tiply Button. This event handler should compute the product of all the values in the Operands list: ListBox and display the result in resultLabel.

g) Running the app. Select Debug > Start Debugging to run your app. Enter two val-ues, then click the Add and Multiply Buttons. Verify that the results displayed are correct. Also, make sure that the Add and Multiply Buttons are not enabled until two values have been entered. Enter a new value and verify that the previous result and the ListBox are cleared. Enter two more values, then click the Add and Multiply Buttons. Verify that the results displayed are correct.

h) Closing the app. Close your running app by clicking its close box.

i) Closing the IDE. Close the Visual Basic IDE by clicking its close box.

Explanation / Answer

vb.net Code:

1. Public Class ArithmeticCalculator
3. Private Property operands As Integer
5. Private Sub enterButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles enterButton.Click
7. Dim operand As Integer
9. If enterOperandTextBox.Text <> String.Empty Then
11. OperandsListBox1.Items.Add(enterOperandTextBox.Text)
12. OperandsListBox1.ClearSelected()
13. enterOperandTextBox.Clear()
15. End If
17. operand = 0
19. If OperandsListBox1.Items.Count = 0 Then
21. enterButton.Enabled = True
22. addButton.Enabled = False
23. multiplyButton.Enabled = False
25. End If
26. End Sub
28. Private Sub addButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles addButton.Click
29. Dim result As Integer
30. Dim operandCounter As Integer
32. result = 0
33. operandCounter = 0
35. Do While operandCounter < OperandsListBox1.Items.Count
36. result = OperandsListBox1.Items(operands)
37. result += operands
38. operandCounter += 1
39. Loop
41. If operandCounter <> 0 Then result = result + OperandsListBox1.Items.Count
43. resultLabel.Text = result
45. End Sub
47. Private Sub multiplyButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles multiplyButton.Click
48. Dim result As Integer
49. Dim operandCounter As Integer
51. result = 0
52. operandCounter = 0
54. Do While operandCounter < OperandsListBox1.Items.Count
55. result = OperandsListBox1.Items(operands)
56. result += operands
57. operandCounter += 1
58. Loop
60. If operandCounter <> 0 Then result = result * OperandsListBox1.Items.Count
61. resultLabel.Text = result
63. End Sub
65. End Class

1. Public Class ArithmeticCalculator
3. Private Property operands As Integer
5. Private Sub enterButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles enterButton.Click
7. Dim operand As Integer
9. If enterOperandTextBox.Text <> String.Empty Then
11. OperandsListBox1.Items.Add(enterOperandTextBox.Text)
12. OperandsListBox1.ClearSelected()
13. enterOperandTextBox.Clear()
15. End If
17. operand = 0
19. If OperandsListBox1.Items.Count = 0 Then
21. enterButton.Enabled = True
22. addButton.Enabled = False
23. multiplyButton.Enabled = False
25. End If
26. End Sub
28. Private Sub addButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles addButton.Click
29. Dim result As Integer
30. Dim operandCounter As Integer
32. result = 0
33. operandCounter = 0
35. Do While operandCounter < OperandsListBox1.Items.Count
36. result = OperandsListBox1.Items(operands)
37. result += operands
38. operandCounter += 1
39. Loop
41. If operandCounter <> 0 Then result = result + OperandsListBox1.Items.Count
43. resultLabel.Text = result
45. End Sub
47. Private Sub multiplyButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles multiplyButton.Click
48. Dim result As Integer
49. Dim operandCounter As Integer
51. result = 0
52. operandCounter = 0
54. Do While operandCounter < OperandsListBox1.Items.Count
55. result = OperandsListBox1.Items(operands)
56. result += operands
57. operandCounter += 1
58. Loop
60. If operandCounter <> 0 Then result = result * OperandsListBox1.Items.Count
61. resultLabel.Text = result
63. End Sub
65. End Class

Public Class ArithmeticCalculator Private Property operands As Integer Private Sub enterButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles enterButton.Click Dim operand As Integer If enterOperandTextBox.Text <> String.Empty Then OperandsListBox1.Items.Add(enterOperandTextBox.Text) OperandsListBox1.ClearSelected() enterOperandTextBox.Clear() End If operand = 0 If OperandsListBox1.Items.Count = 0 Then enterButton.Enabled = True addButton.Enabled = False multiplyButton.Enabled = False End If End Sub Private Sub addButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles addButton.Click Dim result As Integer Dim operandCounter As Integer result = 0 operandCounter = 0 Do While operandCounter < OperandsListBox1.Items.Count result = OperandsListBox1.Items(operands) result += operands operandCounter += 1 Loop If operandCounter <> 0 Then result = result + OperandsListBox1.Items.Count resultLabel.Text = result End Sub Private Sub multiplyButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles multiplyButton.Click Dim result As Integer Dim operandCounter As Integer result = 0 operandCounter = 0 Do While operandCounter < OperandsListBox1.Items.Count result = OperandsListBox1.Items(operands) result += operands operandCounter += 1 Loop If operandCounter <> 0 Then result = result * OperandsListBox1.Items.Count resultLabel.Text = result End Sub End Class

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