Chapter 6

Arrays, Random, Functions, Subroutines

Application #1

Public Class EnhancedCafeteriaSurvey ' two-dimensional array stores voting results Dim votes(3, 1) As Integer

' handles Form's Load event Private Sub EnhancedCafeteriaSurvey_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

foodsComboBox.SelectedIndex = 0 ' select first food in list End Sub ' EnhancedCafeteriaSurvey_Load

Global and Form loads

' handles Vote Button's Click event Private Sub voteButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles voteButton.Click

Dim index As Integer = foodsComboBox.SelectedIndex

' count the vote If likeRadioButton.Checked = True Then votes(index, 0) += 1 Else votes(index, 1) += 1 End If

DisplayVotes() ' display the voting results End Sub ' voteButton_Click

' display the voting results in the ListBox Sub DisplayVotes() resultsListBox.Items.Clear() ' clear the previous results

' display the ListBox header resultsListBox.Items.Add("Menu Item" & vbTab & "Like" & vbTab & "Dislike")

' add voting results for each food option For counter As Integer = 0 To votes.GetUpperBound(0) resultsListBox.Items.Add( foodsComboBox.Items(counter).ToString() & vbTab & votes(counter, 0) & vbTab & votes(counter, 1)) Next End Sub ' DisplayVotes

Function call

' display the voting results in the ListBox Sub DisplayVotes() resultsListBox.Items.Clear() ' clear the previous results

' display the ListBox header resultsListBox.Items.Add("Menu Item" & vbTab & "Like" & vbTab & "Dislike")

' add voting results for each food option For counter As Integer = 0 To votes.GetUpperBound(0) resultsListBox.Items.Add( foodsComboBox.Items(counter).ToString() & vbTab & votes(counter, 0) & vbTab & votes(counter, 1)) Next End Sub ' DisplayVotes

Application #2

Public Class GuessTheNumber Dim randomObject As New Random() Dim number As Integer = randomObject.Next(1, 101)

' handles Enter button click event Private Sub enterButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles enterButton.Click

' retrieve the user's guess Dim guess As Integer = Convert.ToInt32(guessTextBox.Text)

' check answer If guess = number Then outputLabel.Text = "Correct!" enterButton.Enabled = False newGameButton.Enabled = True ElseIf guess > number Then outputLabel.Text = "Too high..." Else outputLabel.Text = "Too low..." End If

guessTextBox.Focus() ' give focus to the TextBox End Sub ' enterButton_Click

Private Sub newGameButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles newGameButton.Click

' start a new game number = randomObject.Next(1, 101) ' generate new number enterButton.Enabled = True ' enable the Enter Button newGameButton.Enabled = False ' disable the New Game Button outputLabel.Text = "" ' clear result guessTextBox.Clear() ' clear the previous guess guessTextBox.Focus() End Sub ' newGameButton_Click

' handles Guess TextBox's TextChanged event Private Sub guessTextBox_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles guessTextBox.TextChanged

outputLabel.Text = String.Empty ' clear result End Sub ' guessTextBox_TextChanged

Public Class RoadSignTest

' String array stores sign names Dim options() As String = { "Do Not Enter", "Narrow bridge", "No bicycles", "No left turn", "No Pedestrians", "No U-turn", "Road Narrows", "Stop", "Stop sign ahead", "Traffic signals ahead", "Winding road ahead", "Yield"}

' Boolean array tracks displayed signs Dim used(options.GetUpperBound(0)) As Boolean

Dim count As Integer = 1 ' number of signs shown Dim correctAnswer As Integer ' index of current sign

' handles Road Sign Test Form's Load event Private Sub RoadSignTest_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

Array.Sort(options) ' alphabetize sign names

' display sign names in ComboBox optionsComboBox.DataSource = options

DisplaySign() ' display first sign in PictureBox End Sub ' RoadSignTest_Load

' display random sign in PictureBox Sub DisplaySign() ' unique index ensures that a sign is used no more than once correctAnswer = GetUniqueRandomNumber() ' retrieve specific image from resources Dim pictureResource = My.Resources.ResourceManager.GetObject("sign" & correctAnswer) signPicture.Image = CType(pictureResource, Image) ' display image End Sub ' DisplaySign

Function GetUniqueRandomNumber() As Integer Dim randomObject As New Random() Dim randomNumber As Integer Do ' generate random numbers until unused sign is found randomNumber = randomObject.Next(0, used.Length) Loop Until used(randomNumber) = False ' indicate that sign has been used used(randomNumber) = True Return randomNumber ' return index for new sign End Function ' GetUniqueRandomNumber

' handles Submit Button's Click event Private Sub submitButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles submitButton.Click

' retrieve answer from ComboBox Dim response As String = Convert.ToString(optionsComboBox.SelectedValue)

' verify answer If response = options(correctAnswer) Then feedBackLabel.Text = "Correct!" Else feedBackLabel.Text = "Incorrect." End If

' inform user if test is over If count >= 5 Then ' test is over feedBackLabel.Text &= " Done!" nextButton.Enabled = False submitButton.Enabled = False optionsComboBox.Enabled = False Else ' test is not over submitButton.Enabled = False nextButton.Enabled = True End If End Sub ' submitButton_Click

' handles Next Sign Button's Click event Private Sub nextButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles nextButton.Click

DisplaySign() ' display next sign feedBackLabel.Text = String.Empty ' clear output

' change selected sign to first in ComboBox optionsComboBox.SelectedIndex = 0

count += 1 ' update number of signs shown

submitButton.Enabled = True nextButton.Enabled = False End Sub ' nextButton_ClickEnd Class ' RoadSignTest