Department of Computer and Mathematical Sciences. Lab 7: Selection

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1 Unit 2: Visual Basic.NET, pages 1 of 11 Department of Computer and Mathematical Sciences CS 1408 Intro to Computer Science with Visual Basic.NET 7 Lab 7: Selection Objectives: The main objective of this lab is to understand how and to use selection controls If-Thenand Select Case Structure in VB.NET. Task 1: Guessing Game The purpose of this task is to learn how to implement If-Then- statement. Statement of the Problem: Create a VB.NET application called Guessing Game that will generate a random number from between 0 and 100. The player/user will enter a guess number in the provided textbox, and then click on the Guess button. If the entered guess number is less than the generated random number, the message Your guess is too low. Try again. is displayed in the designated label. If the entered guess number is greater than the generated random number, the message Your guess is too high. Try again. is displayed. Otherwise, the message Congratulations!!! Your guess is correct. Click on the New Game button to start a new game. is displayed. The New Game button when clicked will start a new game with a new random number. The design/gui of application should look similar to the following figure: Activity 1.1: Create a new project for VB application called Lab7Tsk1 by first create a GUI with the following controls and property settings. Control Name Text ForeColor Font Size Others From1 Default Guessing Game Default None Size: 510, 290 Label1 Default GUESSING GAME Blue 12 Size: 265, 25 Label2 Default Enter Your Guess between 0 and 100: Blue 12 Size: 360, 30 Label3 DisplayLabel None Red 12 Size: 470, 50, BorderStyle: Fixed3D, BackColor: Yellow TextBox InputTextBox None Default 12 Size: 100, 30 Button1 GuessButton Guess Blue 12 Size: 120, 40 Button2 NewGameButton New Game Blue 12 Size: 120, 40 Button3 ExitButton Exit Blue 12 Size: 120, 40 Your GUI of Lab7Tsk1 VB application should look similar to Figure 1.

2 Unit 2: Visual Basic.NET, pages 2 of 11 Figure 1: Lab10Tsk1 Application at Design Time Now we are ready to add code to the Lab7Tsk1 VB application according to statement of the problem. From analyzing the problem, the Lab7Tsk1 VB application has four events and each event has the following actions to be performed: 1. While loading Guessing Game application/form at the start, it will randomly generate a number between 0 and 100 and display the message Start your first guess in the display label. 2. Guess button when clicked will determine whether the number from the InputTextBox is less than, greater than, or equal to the random number. o If it is less than, the message Your guess is too low. Try again. will appear in the display label. o If it is greater than, the message Your guess is too high. Try again. will appear in the display label. o If it is equal to, the message Congratulation!!! Your guess is correct. Click on the New Game button to start a new game. will appear in the display label. 3. New Game button when clicked will randomly generate a number from 0 to 100 and display the message Start your first guess. in the display label. It also clears the InputextBox. 4. Exit button when clicked will close the application. We can organize a chart describes actions to be performed by these four events as follows: Lab10Tsk1 Application Form1 Load Event Generate a random number between 0 and 100 Display the message Start your first guess in the display label. Guess Button Click Event If the guess is less than, the message Your guess is too low. Try again. will appear in the display label. If the guess is greater than, the message Your guess is too high. Try again. will appear in the display label. If the guess is equal to, the message Congratulation!!! Your guess is correct. Click on the New Game button to start a new game. will appear in the display label. New Game Button Click Event Generate a random number between 0 and 100 Display the message Start your first guess in display label. Clear the text in display label. Exit Button Click Event Close the application/window.

3 Lab 7: Selection, page 3 of 11 Activity 1.2: The first event, Form1 load, will load the application/form and while loading the application/form it will 1. Generate a random number between 0 and Display the message Start your first guess. in the display label. This event is called load and the object is being loaded is Form1. The code to generate a random number between 0 and 100 is as follows: REM Initialize random-number generator. Randomize() REM Generate random value between 0 and 100. RandomNumber = CInt(Int((100 * Rnd()))) The code to display the message Start your first guess. in the display label (DiasplayLabel) is as follows: REM Display the message the starting of a game DisplayLabel.Text = "Start your first guess." Insert the above code in the appropriate event procedure that will randomly generate a number from 0 to 100 and display the message Start your first guess in the display label when the form Guessing Game is loaded. Activity 1.3: The New Game Button Click event will perform the following actions: Generate a random number between 0 and 100 Display the message Start your first guess in display label. Clear the text in display label. The code to generate a random number between 0 and 100 is as follows: REM Initialize random-number generator. Randomize() REM Generate random value between 0 and 9. RandomNumber = CInt(Int((100 * Rnd()))) The code to display the message Start your first guess in the display label (DiasplayLabel) is as follows: REM Display the message the starting of a new game DisplayLabel.Text = "Start your first guess." The code to clear the text in the display label (DisplayLabel) is as follows: REM Clear the input in the textbox InputTextBox.Text = "" Insert the above code in the appropriate event procedure that will randomly regenerate a number from 0 to 100, display the message Start your first guess in the display label and clear the InputextBox when the New Game button is clicked. Activity 1.4: The Guess Button Click Event will perform the following actions: If the guess is less than, the message Your guess is too low. Try again. will appear in the display label. If the guess is greater than, the message Your guess is too high. Try again. will appear in the display label. If the guess is equal to, the message Congratulation!!! Your guess is correct. Click on the New Game button to start a new game. will appear in the display label. The code to perform the above task is as follows: REM Assign the value from InputTextBox to the variable Guess. Guess = Val(InputTextBox.Text) This statement initializes Guess to the value from the textbox.

4 Unit 2: Visual Basic.NET, pages 4 of 11 REM Set the focus to InputTextBox and highlight the text in the textbox. InputTextBox.Focus() InputTextBox.SelectAll() These statements set focus and highlight the text in the REM determine whether the Guess is high, low, or correct. If Guess > RandomNumber Then DisplayLabel.Text = "Your guess is too high. Try again." This is a nested if-then-else statement to determine whether If Guess < RandomNumber Then Guess is less than, greater than or equal to RandomNumber. DisplayLabel.Text = "Your guess is too low. Try again." DisplayLabel.Text = "Congratulation!!! Your guess is correct. Click on the New Game button to start a new game." Insert the above code in the appropriate event procedure that will determine whether the number from the InputTextBox is less than, greater than, or equal to the random number and then display appropriate message in the display label when the Guess button is clicked. Activity 1.5: Modified the application Lab7Tsk1 from Activity 1.4 using If-Then- statement such that it will limit the users to only 4 guesses. The appearance of application Lab7Tsk1 at initial run time should look like Figure 2 with the message "You are limited to the maximum of 4 guesses. Start your first guess." in the display label. If the user makes more than 4 guesses, the display should show "Sorry!!! You went over the limit of guesses. Click on the New Game button to start a new game." as shown in Figure 2 and 3. Figure 2: Lab7Tsk1 Application at Initial Run Time Figure 3: Lab7Tsk1 Application When It is Over 4 with 4 guesses limit guesses Hint: use the following declaration of variables in your modification. Const MaxTries As Byte = 4 Dim Tries As Byte You can use the variable Tries to keep track of how many guesses the user has made. Tries must be initialized to 0 when the application is initially loaded and when the New Game button is clicked. Activity 1.6: Modified the application Lab7Tsk1 from Activity 1.5 such that it will limit the users to only 8 guesses. Task 2: Numbers Game The purpose of this task is to learn how to implement nested If-Then- statement. Activity 2.1: Study the following code. This code is a nested If-Then- statement. It will display either The First Message., The Second Message., The Third Message., The Fourth Message., or The Last Message. depends on the values of Integer1 and/or Integer2. If (Integer1 < 0) Or (Integer2 < 0) Then DisplayLabel.Text = "The First Message." Determine where to put these declarations such that more than one events procedure can access these variables.

5 Lab 7: Selection, page 5 of 11 If (Integer2 Mod 2) = 0 Then DisplayLabel.Text = "The Second Message." If (Integer1 \ 3 = 0) And (Integer2 >= 5) Then DisplayLabel.Text = "The Third Message." If Integer2 <> 5 Then DisplayLabel.Text = "The Fourth Message." DisplayLabel.Text = "The Last Message." Complete the following table by filling in with appropriate values of Integer1 and Integer2. Code Integer1 Integer2 Message If (Integer1 < 0) Or (Integer2 < 0) Then DisplayLabel.Text = "The First Message." If (Integer2 Mod 2) = 0 Then DisplayLabel.Text = "The Second Message." If (Integer1\3 = 0) And (Integer2 >= 5) Then DisplayLabel.Text = "The Third Message." If Integer2 <> 5 Then DisplayLabel.Text = "The Fourth Message." DisplayLabel.Text = "The Last Message." Statement of the Problem: Create a VB.NET application called Numbers Game that will list a code of nested If-Then- statement in a list box. The player/user will determine a pair of integers to be entered for each textbox so that when the Enter button is clicked the appropriate message will be displayed in a provided label. The design/gui of application should look similar to the following figure: Activity 2.2: Create a new project for VB application called Lab7Tsk2 by first create a GUI with the following controls and property settings. The First Message. The Second Message. The Third Message. The Fourth Message. The Last Message. Control Name Text ForeColor Font Size Others From1 Default Numbers Game Default None Size: 570, 520 Label1 Default NUMBERS GAME Blue 12 Size: 270, 30 Label2 Default Code Given: Blue 12 Size: 360, 30 Label3 Default Determine two integers that will Blue 12 Size: 510, 30 output each message. Label4 Default Integer 1 Blue 12 Size: 100, 25 Label5 Default Integer 2 Blue 12 Size: 100, 25 Label6 Default Message: Blue 12 Size: 100, 25 Label7 DisplayLabel None Red 12 Size: 410, 30, BorderStyle: Fixed3D, BackColor: Yellow TextBox1 Integer1TextBox None Default 12 Size: 80, 30 TextBox2 Integer2TextBox None Default 12 Size: 80, 30 Button EnterButton Enter Blue 12 Size: 100, 30 ListBox CodeListBox None Default 12 Size: 540, 230 Your GUI of Lab7Tsk2 VB application should look similar to Figure 4.

6 Unit 2: Visual Basic.NET, pages 6 of 11 Figure 4: Lab7Tsk2 Application at Design Time Now we are ready to add code to the Lab7Tsk2 VB application according to statement of the problem. From analyzing the problem, the Lab7Tsk2 VB application has two events and each event has the following actions to be performed: 1. While loading Numbers Game application/form at the start, it will display the code of the nested If-Then- statement in the ListBox as shown in the right figure. 2. Enter button when clicked will Retrieve an integer from each textbox, Integer1 and Integer2 Determine an appropriate message to be displayed according to the two integers: If Integer1 is less than 0 or Integer2 is less than 0, then display the message The First Message. ; otherwise If Integer2 Mod 2 is 0, then display the message The Second Message. ; otherwise If Integer1 divide by 3 is 0 and Integer2 is greater than or equal to 5, then display the message The Third Message. ; otherwise If Integer2 is not equal to 5, then display the message The Fourth Message. ; otherwise, display the message The Last Message. We can organize a chart describes actions to be performed by these two events as follows: Lab9Tsk2 Application Form1 Load Event Display the code of the nested If-Then- statement in the ListBox. Enter Button Click Event Retrieve an integer from each textbox, Integer1 and Integer2 Determine an appropriate message to be displayed according to the two integers: If Integer1 is less than 0 or Integer2 is less than 0, then display the message The First Message. ; otherwise If Integer2 Mod 2 is 0, then display the message The Second Message. ; otherwise If Integer1 divide by 3 is 0 and Integer2 is greater than or equal to 5, then display the message The Third Message. ; otherwise If Integer2 is not equal to 5, then display the message The Fourth Message. ; otherwise, display the message The Last Message.

7 Lab 7: Selection, page 7 of 11 Activity 2.3: The first event, Form1 load, will load the application/form and while loading the application/form it will Display the code of the nested If-Then- statement in the ListBox. The code to display the nested If-Then- statement in the ListBox is: REM Display the code in the ListBox CodeListBox.Items.Add("If (Integer1 < 0) Or (Integer2 < 0) Then") CodeListBox.Items.Add(" DisplayLabel.Text = ""The First Message.""") CodeListBox.Items.Add("If (Integer2 Mod 2) = 0 Then") CodeListBox.Items.Add(" DisplayLabel.Text = ""The Second Message.""") CodeListBox.Items.Add("If (Integer1 \ 3 = 0) And (Integer2 >= 5) Then") CodeListBox.Items.Add(" DisplayLabel.Text = ""The Third Message.""") CodeListBox.Items.Add("If Integer2 <> 5 Then") CodeListBox.Items.Add(" DisplayLabel.Text = ""The Fourth Message.""") CodeListBox.Items.Add("") CodeListBox.Items.Add(" DisplayLabel.Text = ""The Last Message.""") CodeListBox.Items.Add("") Insert the above code in an appropriate event procedure that will display the given nested If- Then- statement in the ListBox when the form Numbers Game is loaded. Activity 2.4: The Enter Button Click event will perform the following actions: Retrieve an integer from each textbox, Integer1 and Integer2 Determine an appropriate message to be displayed according to the two integers: If Integer1 is less than 0 or Integer2 is less than 0, then display the message The First Message. ; otherwise If Integer2 Mod 2 is 0, then display the message The Second Message. ; otherwise If Integer1 divide by 3 is 0 and Integer2 is greater than or equal to 5, then display the message The Third Message. ; otherwise If Integer2 is not equal to 5, then display the message The Fourth Message. ; otherwise, display the message The Last Message. The code to perform the above actions is as follows: Dim Integer1, Integer2 As Integer REM Assign values from Textboxes to Integer1 and Integer2 Integer1 = Val(Integer1TextBox.Text) Integer2 = Val(Integer2TextBox.Text) REM Nested if-then-else If (Integer1 < 0) Or (Integer2 < 0) Then DisplayLabel.Text = "The First Message." If (Integer2 Mod 2) = 0 Then DisplayLabel.Text = "The Second Message." If (Integer1 \ 3 = 0) And (Integer2 >= 5) Then DisplayLabel.Text = "The Third Message." If Integer2 <> 5 Then DisplayLabel.Text = "The Fourth Message." DisplayLabel.Text = "The Last Message." REM Set focus to Integer1TextBox Integer1TextBox.Focus() Integer1TextBox.SelectAll() End Sub

8 Unit 2: Visual Basic.NET, pages 8 of 11 Insert the above code in the appropriate event procedure that will display a message in the display label when the Enter button is clicked. Activity 2.5: Run the application Lab7Tsk2 and verify your answer in Activity 2.1. Code Integer1 Integer2 Message If (Integer1 < 0) Or (Integer2 < 0) Then DisplayLabel.Text = "The First Message." If (Integer2 Mod 2) = 0 Then DisplayLabel.Text = "The Second Message." If (Integer1\3 = 0) And (Integer2 >= 5) Then DisplayLabel.Text = "The Third Message." If Integer2 <> 5 Then DisplayLabel.Text = "The Fourth Message." DisplayLabel.Text = "The Last Message." The First Message. The Second Message. The Third Message. The Fourth Message. The Last Message. Task 3: Tax Rate The purpose of this task is to learn how to implement Select-Case statement. The Select-Case structure is an alternative to the If-Then-If structure. The syntax of the Select-Case construct is as follows: Select Case expression Case value_1 statement(s) Case value_2 statement(s)... Case value_n statement(s) Case statement(s) End Select The following is the same example where one using If-Then-If structure and the other using Select-Case structure. The Select-Case structure is more organized and is easy to understand. If (creditsearned >= 90) Then DisplayLabel.Text = SENIOR STATUS If (creditsearned >= 60) Then DisplayLabel.Text = JUNIOR STATUS IF (creditsearned >= 30) Then DisplayLabel.Text = SOPHOMORE STATUS DisplayLabel.Text = FRESHMAN STATUS Statement of the Problem: Create a VB.NET application called 2005 Tax Rate that will estimate income tax paid for either single or married according to their income. The design/gui of application should look similar to the following figure: Activity 3.1: Create a VB application called Lab7Tsk3 by first create a GUI with the following controls and property settings. Select Case creditsearned Case Is >= 90 Is refer to creditsearned DisplayLabel.Text = SENIOR STATUS Case 60 to 89 DisplayLabel.Text = JUNIOR STATUS Case 30 to 59 DisplayLabel.Text = SOPHOMORE STATUS Case DisplayLabel.Text = FRESHMAN STATUS End Select

9 Lab 7: Selection, page 9 of 11 Control Name Text ForeColor Font Size Others From1 Default 2005 Tax Rate Default None Size: 510, 290 Label1 Default 2005 ESTIMATED TAX RATE Blue 12 Size: 300, 30, Bold: True Label2 Default Enter Your Income: Blue 12 Size: 190, 30 Label3 Default Estimated Tax Paid: Blue 12 Size: 190, 30 Size: 250, 30, BorderStyle: Label4 DisplayLabel None Red 12 Fixed3D, BackColor: Yellow TextBox IncomeTextBox None Default 12 Size: 190, 30 RadioButton1 SingleRadioButton Single Blue 12 Size: 90, 30, Checked: True RadioButton2 MarriedRadioButton Married Filing Jointly Blue 12 Size: 220, 30 Button EnterButton Enter Blue 12 Size: 120, 40 Your GUI of Lab7Tsk3 VB application should look similar to Figure 5. Figure 5: Lab7Tsk3 Application at Design Time According to the following 2005 Tax Rate from Internal Revenue Service Web site, the estimated income tax paid can be computed using the tables given below. One is for single and the other is for married couple filing joint return Tax Rate Schedules Note: These tax rate schedules are provided so that you can compute your estimated tax for To compute your actual income tax, please see the instructions for 2005 Form 1040, 1040A, or 1040EZ as appropriate when they are available. Schedule X Single If taxable income is over-- But not over-- The tax is: $0 $7,300 10% of the amount over $0 $7,300 $29,700 $730 plus 15% of the amount over 7,300 $29,700 $71,950 $4, plus 25% of the amount over 29,700 $71,950 $150,150 $14, plus 28% of the amount over 71,950 $150,150 $326,450 $36, plus 33% of the amount over 150,150 $326,450 no limit $94, plus 35% of the amount over 326,450 Schedule Y-1 Married Filing Jointly or Qualifying Widow(er) If taxable income is over-- But not over-- The tax is: $0 $14,600 10% of the amount over $0 $14,600 $59,400 $1, plus 15% of the amount over 14,600 $59,400 $119,950 $8,180 plus 25% of the amount over 59,400 $119,950 $182,800 $23, plus 28% of the amount over 119,950 $182,800 $326,450 $40, plus 33% of the amount over 182,800 $326,450 no limit $88, plus 35% of the amount over 326,450 Now we are ready to add code to the Lab7Tsk3 VB application according to statement of the problem. From analyzing the problem, the Lab7Tsk2 VB application has only one event and this event has the following actions to be performed: Enter button when clicked will Retrieve the value from the IncomeTextBox

10 Unit 2: Visual Basic.NET, pages 10 of 11 Compute the estimated tax paid based on the entered valued in the textbox and whether SingleRadioButton or MarriedRadioButton is selected. Display estimated tax paid in the display label. We can organize a chart describes actions to be performed by this event as follows: Lab9Tsk3 Application Enter Button Click Event Retrieve the value from the IncomeTextBox Compute the estimated tax paid based on the entered valued in the textbox and whether SingleRadioButton or MarriedRadioButton is selected. Display estimated tax paid in the display label. Activity 3.2: The Enter button click event will perform the following actions: Retrieve the value from the IncomeTextBox Compute the estimated tax paid based on the entered valued in the textbox and whether SingleRadioButton or MarriedRadioButton is selected. Display estimated tax paid in the display label. The code to retrieve the value from the IncomeTextBox is as follws: Dim Income As Integer Dim TaxPaid As Double REM Assign Income to the number from IncomeTextBox Income = IncomeTextBox.Text The code to Compute the estimated tax paid based on the entered valued in the textbox and whether SingleRadioButton or MarriedRadioButton is selected. REM Check whether it is single filing or marries filing jointly If SingleRadioButton.Checked Then REM Compute the tax paid for single If Income <= 7300 Then TaxPaid = 0.1 * Income If Income > 7300 And Income <= Then TaxPaid = 0.15 * (Income 7300) If Income > And Income <= Then TaxPaid = 0.25 * (Income 29700) If Income > And Income <= Then TaxPaid = 0.28 * (Income 71950) If Income > And Income <= Then TaxPaid = 0.33 * (Income ) TaxPaid = 0.35 * (Income ) REM Compute the tax paid for single If Income <= Then TaxPaid = 0.1 * Income If Income > And Income <= Then TaxPaid = 0.15 * (Income 14600) If Income > And Income <= Then TaxPaid = 0.25 * (Income 59400) If Income > And Income <= Then TaxPaid = 0.28 * (Income ) If Income > And Income <= Then TaxPaid = 0.33 * (Income ) TaxPaid = 0.35 * (Income ) The code to display estimated tax paid in the display label. REM Display tax paid DisplayLabel.Text = FormatCurrency(TaxPaid)

11 Lab 7: Selection, page 11 of 11 Insert the above code in the appropriate event procedure that will display a message in the display label when the Enter button is clicked. Activity 3.3: Replace only nested If-Then-If statements (there are two of them) in Activity 3.2 with Select-Case statements.