Program Plan 1. Below mentioned variables are used lstGrades − Listbox that holds the values of grades lstNames − Listbox that holds the name of students who acquired the selected grade in lstGrades. lblNumber − Displays the number of students listed in lstNames sel_Grade − Selected Item in lstGrades. 2. Functions mentioned below are used: lstGrades_SelectedIndexChanged()-Called when user selects an item from the listbox lstGrades. frmMain_Load()-Called when a solution is executed and form Main is loaded. btnDisplay_Click()- Called when the user clicks on the button Display. btnExit_Click()- Called when the user clicks on the Exit button to close the application. Program Description: To change the two parallel arrays in the earlier application with a two-dimensional array and the procedure code of the btnDisplay_Click. Program ' Name: Professor Juarez Project ' Purpose: Display the names and number of students earning a specific grade. ' Programmer: <your name> on <current date> Option Explicit On Option Strict On Option Infer Off Public Class frmMain Private Sub btnExit_Click(sender As Object, e As EventArgs) Handles btnExit.Click Me.Close() End Sub Private Sub btnDisplay_Click(sender As Object, e As EventArgs) Handles btnDisplay.Click ' Display the names and number of students earning a specific grade. 'Modified Two dimensional array strStudents(,) Dim strStudents(,) As String = {{"Helen", "A"}, {"Peter", "B"}, {"Yolanda", "B"}, {"Carl", "A"}, {"Jennifer", "D"}, {"Charles", "F"}, {"Addison", "A"}, {"Aiden", "B"}, {"Treyson", "A"}, {"Sydney", "B"}, {"Jacob", "F"}, {"Nancy", "C"}, {"George", "C"}, {"Ursula", "B"}, {"Jack", "D"}} Dim sel_Grade As String Dim no_of_Students As Integer = 0 sel_Grade = lstGrades.SelectedItem.ToString() 'Get the number of rows in two dimensional array Dim noofrows As Integer = strStudents.GetUpperBound(0) For row As Integer = 0 To noofrows 'Searches the grades (col = 1) in all the rows If sel_Grade = strStudents(row, 1) Then 'Add the names in col 0 to lstNames lstNames.Items.Add(strStudents(row, 0)) no_of_Students += 1 End If Next row lblNumber.Text = no_of_Students.ToString() End Sub Private Sub frmMain_Load(sender As Object, e As EventArgs) Handles MyBase.Load 'set the first item in lstGrades as selected Index lstGrades.SelectedIndex = 0 End Sub Private Sub lstGrades_SelectedIndexChanged(sender As Object, e As EventArgs) Handles lstGrades.SelectedIndexChanged 'clears the text of lblNumber and all items of lstNames lblNumber.Text = "" lstNames.Items.Clear() End Sub End Class Form Design: Designed form is shown below. Sample output for the original program When the program is just started the following form will be loaded. When the user selects an item from lstGrades and clicks on Display button, then the following changes are made. When the user presses the Exit button, the application will quit. Explanation: This program is for traversing a two-dimensional array strStudents() which has the student names and student grades as two columns. When a user selects a grade from the list box lstGrades then student names who have secured that grade are shown on the list box lstNames and the number is shown in lblNumber. When the user clicks on the Exit button, the application will be closed.

Chapter 8 Solutions