' cd assignment adjusted to use array of structure instead of paralelel arrays 
' also, writes sales to file - to illustrate passing a structure to a procedure
Option Explicit On 
Option Strict On
Public Class Form1
    Inherits System.Windows.Forms.Form

#Region " Windows Form Designer generated code "

    Public Sub New()
        MyBase.New()

        'This call is required by the Windows Form Designer.
        InitializeComponent()

        'Add any initialization after the InitializeComponent() call

    End Sub

    'Form overrides dispose to clean up the component list.
    Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing Then
            If Not (components Is Nothing) Then
                components.Dispose()
            End If
        End If
        MyBase.Dispose(disposing)
    End Sub

    'Required by the Windows Form Designer
    Private components As System.ComponentModel.IContainer

    'NOTE: The following procedure is required by the Windows Form Designer
    'It can be modified using the Windows Form Designer.  
    'Do not modify it using the code editor.
    Friend WithEvents Label1 As System.Windows.Forms.Label
    Friend WithEvents GroupBox1 As System.Windows.Forms.GroupBox
    Friend WithEvents LstCD As System.Windows.Forms.ListBox
    Friend WithEvents Label2 As System.Windows.Forms.Label
    Friend WithEvents Label3 As System.Windows.Forms.Label
    Friend WithEvents TxtCD As System.Windows.Forms.TextBox
    Friend WithEvents TxtArtist As System.Windows.Forms.TextBox
    Friend WithEvents Label4 As System.Windows.Forms.Label
    Friend WithEvents TxtPrice As System.Windows.Forms.TextBox
    Friend WithEvents Label5 As System.Windows.Forms.Label
    Friend WithEvents TxtTax As System.Windows.Forms.TextBox
    Friend WithEvents Label6 As System.Windows.Forms.Label
    Friend WithEvents TxtTotal As System.Windows.Forms.TextBox
    Friend WithEvents Label7 As System.Windows.Forms.Label
    Friend WithEvents BtnBuy As System.Windows.Forms.Button
    Friend WithEvents BtnClear As System.Windows.Forms.Button
    Friend WithEvents TxtInv As System.Windows.Forms.TextBox
    Friend WithEvents Label8 As System.Windows.Forms.Label
    Friend WithEvents GroupBox2 As System.Windows.Forms.GroupBox
    Friend WithEvents BtnInv As System.Windows.Forms.Button
    Friend WithEvents BtnSummary As System.Windows.Forms.Button
    Friend WithEvents BtnQuit As System.Windows.Forms.Button
    Friend WithEvents TxtRev As System.Windows.Forms.TextBox
    Friend WithEvents Label9 As System.Windows.Forms.Label
    Friend WithEvents TxtTop As System.Windows.Forms.TextBox
    Friend WithEvents Label10 As System.Windows.Forms.Label
    Friend WithEvents TxtTopArtist As System.Windows.Forms.TextBox
    Friend WithEvents Label11 As System.Windows.Forms.Label
    Friend WithEvents LstInv As System.Windows.Forms.ListBox
    Friend WithEvents BtnInClass As System.Windows.Forms.Button
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        Me.Label1 = New System.Windows.Forms.Label
        Me.GroupBox1 = New System.Windows.Forms.GroupBox
        Me.TxtInv = New System.Windows.Forms.TextBox
        Me.Label8 = New System.Windows.Forms.Label
        Me.BtnClear = New System.Windows.Forms.Button
        Me.BtnBuy = New System.Windows.Forms.Button
        Me.TxtTotal = New System.Windows.Forms.TextBox
        Me.Label7 = New System.Windows.Forms.Label
        Me.TxtTax = New System.Windows.Forms.TextBox
        Me.Label6 = New System.Windows.Forms.Label
        Me.TxtPrice = New System.Windows.Forms.TextBox
        Me.Label5 = New System.Windows.Forms.Label
        Me.TxtArtist = New System.Windows.Forms.TextBox
        Me.Label4 = New System.Windows.Forms.Label
        Me.TxtCD = New System.Windows.Forms.TextBox
        Me.Label3 = New System.Windows.Forms.Label
        Me.Label2 = New System.Windows.Forms.Label
        Me.LstCD = New System.Windows.Forms.ListBox
        Me.GroupBox2 = New System.Windows.Forms.GroupBox
        Me.LstInv = New System.Windows.Forms.ListBox
        Me.Label11 = New System.Windows.Forms.Label
        Me.TxtTopArtist = New System.Windows.Forms.TextBox
        Me.TxtTop = New System.Windows.Forms.TextBox
        Me.Label10 = New System.Windows.Forms.Label
        Me.TxtRev = New System.Windows.Forms.TextBox
        Me.Label9 = New System.Windows.Forms.Label
        Me.BtnInv = New System.Windows.Forms.Button
        Me.BtnSummary = New System.Windows.Forms.Button
        Me.BtnQuit = New System.Windows.Forms.Button
        Me.BtnInClass = New System.Windows.Forms.Button
        Me.GroupBox1.SuspendLayout()
        Me.GroupBox2.SuspendLayout()
        Me.SuspendLayout()
        '
        'Label1
        '
        Me.Label1.AutoSize = True
        Me.Label1.Font = New System.Drawing.Font("Microsoft Sans Serif", 18.0!, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.Label1.Location = New System.Drawing.Point(193, 21)
        Me.Label1.Name = "Label1"
        Me.Label1.Size = New System.Drawing.Size(122, 31)
        Me.Label1.TabIndex = 0
        Me.Label1.Text = "CDs R Us"
        '
        'GroupBox1
        '
        Me.GroupBox1.Controls.Add(Me.TxtInv)
        Me.GroupBox1.Controls.Add(Me.Label8)
        Me.GroupBox1.Controls.Add(Me.BtnClear)
        Me.GroupBox1.Controls.Add(Me.BtnBuy)
        Me.GroupBox1.Controls.Add(Me.TxtTotal)
        Me.GroupBox1.Controls.Add(Me.Label7)
        Me.GroupBox1.Controls.Add(Me.TxtTax)
        Me.GroupBox1.Controls.Add(Me.Label6)
        Me.GroupBox1.Controls.Add(Me.TxtPrice)
        Me.GroupBox1.Controls.Add(Me.Label5)
        Me.GroupBox1.Controls.Add(Me.TxtArtist)
        Me.GroupBox1.Controls.Add(Me.Label4)
        Me.GroupBox1.Controls.Add(Me.TxtCD)
        Me.GroupBox1.Controls.Add(Me.Label3)
        Me.GroupBox1.Controls.Add(Me.Label2)
        Me.GroupBox1.Controls.Add(Me.LstCD)
        Me.GroupBox1.Location = New System.Drawing.Point(27, 62)
        Me.GroupBox1.Name = "GroupBox1"
        Me.GroupBox1.Size = New System.Drawing.Size(513, 340)
        Me.GroupBox1.TabIndex = 1
        Me.GroupBox1.TabStop = False
        Me.GroupBox1.Text = "Purchase"
        '
        'TxtInv
        '
        Me.TxtInv.Location = New System.Drawing.Point(367, 146)
        Me.TxtInv.Name = "TxtInv"
        Me.TxtInv.ReadOnly = True
        Me.TxtInv.Size = New System.Drawing.Size(126, 20)
        Me.TxtInv.TabIndex = 15
        Me.TxtInv.Text = ""
        '
        'Label8
        '
        Me.Label8.Font = New System.Drawing.Font("Microsoft Sans Serif", 10.2!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.Label8.Location = New System.Drawing.Point(273, 146)
        Me.Label8.Name = "Label8"
        Me.Label8.Size = New System.Drawing.Size(94, 20)
        Me.Label8.TabIndex = 14
        Me.Label8.Text = "Inventory:"
        '
        'BtnClear
        '
        Me.BtnClear.Location = New System.Drawing.Point(380, 284)
        Me.BtnClear.Name = "BtnClear"
        Me.BtnClear.Size = New System.Drawing.Size(87, 35)
        Me.BtnClear.TabIndex = 13
        Me.BtnClear.Text = "Clear"
        '
        'BtnBuy
        '
        Me.BtnBuy.Location = New System.Drawing.Point(273, 284)
        Me.BtnBuy.Name = "BtnBuy"
        Me.BtnBuy.Size = New System.Drawing.Size(87, 35)
        Me.BtnBuy.TabIndex = 12
        Me.BtnBuy.Text = "Buy"
        '
        'TxtTotal
        '
        Me.TxtTotal.Location = New System.Drawing.Point(367, 222)
        Me.TxtTotal.Name = "TxtTotal"
        Me.TxtTotal.ReadOnly = True
        Me.TxtTotal.Size = New System.Drawing.Size(126, 20)
        Me.TxtTotal.TabIndex = 11
        Me.TxtTotal.Text = ""
        '
        'Label7
        '
        Me.Label7.Font = New System.Drawing.Font("Microsoft Sans Serif", 10.2!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.Label7.Location = New System.Drawing.Point(273, 222)
        Me.Label7.Name = "Label7"
        Me.Label7.Size = New System.Drawing.Size(94, 21)
        Me.Label7.TabIndex = 10
        Me.Label7.Text = "Total:"
        '
        'TxtTax
        '
        Me.TxtTax.Location = New System.Drawing.Point(367, 180)
        Me.TxtTax.Name = "TxtTax"
        Me.TxtTax.ReadOnly = True
        Me.TxtTax.Size = New System.Drawing.Size(126, 20)
        Me.TxtTax.TabIndex = 9
        Me.TxtTax.Text = ""
        '
        'Label6
        '
        Me.Label6.Font = New System.Drawing.Font("Microsoft Sans Serif", 10.2!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.Label6.Location = New System.Drawing.Point(273, 180)
        Me.Label6.Name = "Label6"
        Me.Label6.Size = New System.Drawing.Size(94, 21)
        Me.Label6.TabIndex = 8
        Me.Label6.Text = "Tax:"
        '
        'TxtPrice
        '
        Me.TxtPrice.Location = New System.Drawing.Point(367, 111)
        Me.TxtPrice.Name = "TxtPrice"
        Me.TxtPrice.ReadOnly = True
        Me.TxtPrice.Size = New System.Drawing.Size(126, 20)
        Me.TxtPrice.TabIndex = 7
        Me.TxtPrice.Text = ""
        '
        'Label5
        '
        Me.Label5.Font = New System.Drawing.Font("Microsoft Sans Serif", 10.2!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.Label5.Location = New System.Drawing.Point(273, 111)
        Me.Label5.Name = "Label5"
        Me.Label5.Size = New System.Drawing.Size(94, 21)
        Me.Label5.TabIndex = 6
        Me.Label5.Text = "CD Price:"
        '
        'TxtArtist
        '
        Me.TxtArtist.Location = New System.Drawing.Point(367, 76)
        Me.TxtArtist.Name = "TxtArtist"
        Me.TxtArtist.ReadOnly = True
        Me.TxtArtist.Size = New System.Drawing.Size(126, 20)
        Me.TxtArtist.TabIndex = 5
        Me.TxtArtist.Text = ""
        '
        'Label4
        '
        Me.Label4.Font = New System.Drawing.Font("Microsoft Sans Serif", 10.2!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.Label4.Location = New System.Drawing.Point(273, 76)
        Me.Label4.Name = "Label4"
        Me.Label4.Size = New System.Drawing.Size(94, 21)
        Me.Label4.TabIndex = 4
        Me.Label4.Text = "CD Artist:"
        '
        'TxtCD
        '
        Me.TxtCD.Location = New System.Drawing.Point(367, 42)
        Me.TxtCD.Name = "TxtCD"
        Me.TxtCD.ReadOnly = True
        Me.TxtCD.Size = New System.Drawing.Size(126, 20)
        Me.TxtCD.TabIndex = 3
        Me.TxtCD.Text = ""
        '
        'Label3
        '
        Me.Label3.Font = New System.Drawing.Font("Microsoft Sans Serif", 10.2!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.Label3.Location = New System.Drawing.Point(273, 42)
        Me.Label3.Name = "Label3"
        Me.Label3.Size = New System.Drawing.Size(94, 20)
        Me.Label3.TabIndex = 2
        Me.Label3.Text = "CD Title:"
        '
        'Label2
        '
        Me.Label2.Location = New System.Drawing.Point(20, 28)
        Me.Label2.Name = "Label2"
        Me.Label2.Size = New System.Drawing.Size(173, 21)
        Me.Label2.TabIndex = 1
        Me.Label2.Text = "Choose CD:"
        '
        'LstCD
        '
        Me.LstCD.Location = New System.Drawing.Point(20, 55)
        Me.LstCD.Name = "LstCD"
        Me.LstCD.Size = New System.Drawing.Size(227, 251)
        Me.LstCD.TabIndex = 0
        '
        'GroupBox2
        '
        Me.GroupBox2.Controls.Add(Me.LstInv)
        Me.GroupBox2.Controls.Add(Me.Label11)
        Me.GroupBox2.Controls.Add(Me.TxtTopArtist)
        Me.GroupBox2.Controls.Add(Me.TxtTop)
        Me.GroupBox2.Controls.Add(Me.Label10)
        Me.GroupBox2.Controls.Add(Me.TxtRev)
        Me.GroupBox2.Controls.Add(Me.Label9)
        Me.GroupBox2.Location = New System.Drawing.Point(560, 69)
        Me.GroupBox2.Name = "GroupBox2"
        Me.GroupBox2.Size = New System.Drawing.Size(300, 423)
        Me.GroupBox2.TabIndex = 2
        Me.GroupBox2.TabStop = False
        Me.GroupBox2.Text = "Management"
        '
        'LstInv
        '
        Me.LstInv.Location = New System.Drawing.Point(27, 180)
        Me.LstInv.Name = "LstInv"
        Me.LstInv.Size = New System.Drawing.Size(260, 199)
        Me.LstInv.TabIndex = 10
        '
        'Label11
        '
        Me.Label11.Font = New System.Drawing.Font("Microsoft Sans Serif", 10.2!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.Label11.Location = New System.Drawing.Point(20, 146)
        Me.Label11.Name = "Label11"
        Me.Label11.Size = New System.Drawing.Size(207, 20)
        Me.Label11.TabIndex = 9
        Me.Label11.Text = "Inventory:"
        '
        'TxtTopArtist
        '
        Me.TxtTopArtist.Location = New System.Drawing.Point(140, 111)
        Me.TxtTopArtist.Name = "TxtTopArtist"
        Me.TxtTopArtist.ReadOnly = True
        Me.TxtTopArtist.Size = New System.Drawing.Size(127, 20)
        Me.TxtTopArtist.TabIndex = 8
        Me.TxtTopArtist.Text = ""
        '
        'TxtTop
        '
        Me.TxtTop.Location = New System.Drawing.Point(140, 83)
        Me.TxtTop.Name = "TxtTop"
        Me.TxtTop.ReadOnly = True
        Me.TxtTop.Size = New System.Drawing.Size(127, 20)
        Me.TxtTop.TabIndex = 7
        Me.TxtTop.Text = ""
        '
        'Label10
        '
        Me.Label10.Font = New System.Drawing.Font("Microsoft Sans Serif", 10.2!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.Label10.Location = New System.Drawing.Point(20, 83)
        Me.Label10.Name = "Label10"
        Me.Label10.Size = New System.Drawing.Size(107, 21)
        Me.Label10.TabIndex = 6
        Me.Label10.Text = "Top Seller:"
        '
        'TxtRev
        '
        Me.TxtRev.Location = New System.Drawing.Point(140, 49)
        Me.TxtRev.Name = "TxtRev"
        Me.TxtRev.ReadOnly = True
        Me.TxtRev.Size = New System.Drawing.Size(127, 20)
        Me.TxtRev.TabIndex = 5
        Me.TxtRev.Text = ""
        '
        'Label9
        '
        Me.Label9.Font = New System.Drawing.Font("Microsoft Sans Serif", 10.2!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.Label9.Location = New System.Drawing.Point(20, 49)
        Me.Label9.Name = "Label9"
        Me.Label9.Size = New System.Drawing.Size(107, 20)
        Me.Label9.TabIndex = 4
        Me.Label9.Text = "Total Revenues:"
        '
        'BtnInv
        '
        Me.BtnInv.Location = New System.Drawing.Point(140, 437)
        Me.BtnInv.Name = "BtnInv"
        Me.BtnInv.Size = New System.Drawing.Size(87, 34)
        Me.BtnInv.TabIndex = 16
        Me.BtnInv.Text = "Inventory"
        '
        'BtnSummary
        '
        Me.BtnSummary.Location = New System.Drawing.Point(47, 437)
        Me.BtnSummary.Name = "BtnSummary"
        Me.BtnSummary.Size = New System.Drawing.Size(86, 34)
        Me.BtnSummary.TabIndex = 15
        Me.BtnSummary.Text = "Summary"
        '
        'BtnQuit
        '
        Me.BtnQuit.Location = New System.Drawing.Point(240, 437)
        Me.BtnQuit.Name = "BtnQuit"
        Me.BtnQuit.Size = New System.Drawing.Size(87, 34)
        Me.BtnQuit.TabIndex = 17
        Me.BtnQuit.Text = "Quit"
        '
        'BtnInClass
        '
        Me.BtnInClass.Location = New System.Drawing.Point(80, 24)
        Me.BtnInClass.Name = "BtnInClass"
        Me.BtnInClass.Size = New System.Drawing.Size(64, 32)
        Me.BtnInClass.TabIndex = 18
        Me.BtnInClass.Text = "Summary"
        '
        'Form1
        '
        Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
        Me.AutoScroll = True
        Me.ClientSize = New System.Drawing.Size(612, 433)
        Me.Controls.Add(Me.BtnInClass)
        Me.Controls.Add(Me.BtnQuit)
        Me.Controls.Add(Me.BtnInv)
        Me.Controls.Add(Me.BtnSummary)
        Me.Controls.Add(Me.GroupBox2)
        Me.Controls.Add(Me.GroupBox1)
        Me.Controls.Add(Me.Label1)
        Me.Name = "Form1"
        Me.Text = "Form1"
        Me.GroupBox1.ResumeLayout(False)
        Me.GroupBox2.ResumeLayout(False)
        Me.ResumeLayout(False)

    End Sub

#End Region

    Structure cd
        Public title As String
        Public artist As String
        Public price As Double
        Public inventory As Integer
        Public sold As Integer
        Public revenues As Double
    End Structure
    Dim inpf As IO.StreamReader
    Dim outpf As IO.StreamWriter
    Dim numCD As Integer = 0
    Const arraySize As Integer = 40
    Const taxRate As Double = 0.07
    Dim CDs(arraySize) As cd 

    Private Sub clearText()
        TxtCD.Text = ""
        TxtArtist.Text = ""
        TxtPrice.Text = ""
        TxtTax.Text = ""
        TxtInv.Text = ""
        TxtTotal.Text = ""
    End Sub

    ' sorts the array of cd structures based on inventory (high to low)
    Private Sub sortStructByInventory(ByRef array() As cd, ByVal num As Integer)
        Dim outer As Integer
        Dim inner As Integer
        Dim posOfLarge As Integer
        Dim temp As cd
        ' loop through all but last position of the array
        ' each time, place the largest remaining inventory into the current position
        For outer = 0 To (num - 2)
            posOfLarge = outer    ' default to largest being first
            ' loop through remaining cds finding the largest inventory
            For inner = outer + 1 To (num - 1)
                If array(inner).inventory > array(posOfLarge).inventory Then
                    ' new largest - update position of largest
                    posOfLarge = inner
                End If
            Next inner
            ' determine if a swap is needed
            If posOfLarge <> outer Then
                temp = array(posOfLarge)
                array(posOfLarge) = array(outer)
                array(outer) = temp
            End If
        Next outer

    End Sub

    ' ensure that list box is in synch with array
    Private Sub refreshList(ByVal array() As cd, ByVal num As Integer)
        Dim cnt As Integer
        LstCD.Items.Clear()

        For cnt = 0 To num - 1
            ' here's an idea - don't show out of stock CDs
            If array(cnt).inventory > 0 Then
                LstCD.Items.Add(array(cnt).title & " " & array(cnt).artist & " " & array(cnt).price)
            End If
        Next cnt
    End Sub

    Private Sub sortCDsNRefreshList(ByRef array() As cd, ByVal num As Integer)
        sortStructByInventory(array, num)
        refreshList(array, num)
    End Sub

    Private Sub writeSale(ByVal currCd As cd, ByVal outf As IO.StreamWriter)
        outf.WriteLine(currCd.title & "," & currCd.artist & "," & _
            currCd.price.ToString("C") & "," & currCd.inventory & "," & _
            currCd.sold & "," & currCd.revenues)
    End Sub

    Private Sub getCD(ByVal currStr As String, ByRef currCD As cd)
        currStr = inpf.ReadLine()
        ' all of the following assumes input file in correct format - title,artist,price,inventory
        Dim commapos As Integer
        commapos = currStr.IndexOf(",")
        currCD.title = currStr.Substring(0, commapos)
        currStr = currStr.Substring(commapos + 1)
        commapos = currStr.IndexOf(",")
        currCD.artist = currStr.Substring(0, commapos)
        currStr = currStr.Substring(commapos + 1)
        commapos = currStr.IndexOf(",")
        currCD.price = Convert.ToDouble(currStr.Substring(0, commapos))
        currStr = currStr.Substring(commapos + 1)
        currCD.inventory = Convert.ToInt32(currStr)

    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        If IO.File.Exists("CDs.txt") Then
            inpf = IO.File.OpenText("CDs.txt")
            Do While inpf.Peek <> -1 And numCD <= arraySize
                Dim currLine As String
                getCD(currLine, CDs(numCD))
                CDs(numCD).sold = 0
                CDs(numCD).revenues = 0
                LstCD.Items.Add(CDs(numCD).title & " " & CDs(numCD).artist & " " & CDs(numCD).price)
                numCD = numCD + 1
            Loop
        End If
    End Sub

    Private Sub BtnClear_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnClear.Click


        clearText()

    End Sub

    Private Sub BtnQuit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnQuit.Click
        Me.Close()

    End Sub

    Private Sub BtnBuy_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnBuy.Click
        ' when buying - need to update inventory, number sold and revenues arrays
        Dim chosen As Integer
        chosen = LstCD.SelectedIndex
        If chosen >= 0 AndAlso CDs(chosen).inventory > 0 Then
            'can sell it
            CDs(chosen).inventory = CDs(chosen).inventory - 1
            CDs(chosen).sold = CDs(chosen).sold + 1
            CDs(chosen).revenues = CDs(chosen).revenues + Convert.ToDouble(TxtTotal.Text.TrimStart("$"c).Trim(","c))

            ' write to file
            outpf = IO.File.AppendText("sales.txt")
            writeSale(CDs(chosen), outpf)
            outpf.Close()

            ' clear text boxes and thank buyer
            MsgBox("thank you, please come again")
            clearText()

        Else
            If chosen < 0 Then
                MsgBox("please select a CD to buy first")
            Else
                MsgBox("Purchase not successful, CD is out of stock")
            End If
        End If

    End Sub

    Private Sub LstCD_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles LstCD.SelectedIndexChanged
        ' get needed info from arrays
        Dim chosen As Integer
        chosen = LstCD.SelectedIndex
        TxtCD.Text = CDs(chosen).title
        TxtArtist.Text = CDs(chosen).artist
        TxtPrice.Text = CDs(chosen).price.ToString("c")
        TxtInv.Text = CDs(chosen).inventory.ToString("n0")
        Dim tax As Double
        tax = CDs(chosen).price * taxRate
        TxtTax.Text = tax.ToString("c")
        Dim total As Double
        total = CDs(chosen).price + tax
        TxtTotal.Text = total.ToString("c")
    End Sub

    Private Sub BtnSummary_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnSummary.Click
        ' find top seller - by number sold
        ' and total revenues
        Dim cnt As Integer
        Dim maxSold As Integer = 0
        Dim maxCDNum As Integer = 0
        Dim totalRevenues As Double = 0
        For cnt = 0 To numCD - 1
            If CDs(cnt).sold > maxSold Then
                ' new top seller
                maxSold = CDs(cnt).sold
                maxCDNum = cnt

            End If
            totalRevenues = totalRevenues + CDs(cnt).revenues
        Next
        TxtRev.Text = totalRevenues.ToString("C")
        TxtTop.Text = CDs(maxCDNum).title
        TxtTopArtist.Text = CDs(maxCDNum).artist
    End Sub

    Private Sub BtnInv_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnInv.Click

        ' sord array by inventory and refresh list box of cds
        sortCDsNRefreshList(CDs, numCD)
        ' clear previous inventory list
        LstInv.Items.Clear()
        Dim cnt As Integer
        ' show inventory for all cds
        For cnt = 0 To numCD - 1
            Dim curr As String
            curr = CDs(cnt).title & " " & CDs(cnt).artist & " " & CDs(cnt).inventory
            LstInv.Items.Add(curr)

        Next
    End Sub

    Private Sub BtnInClass_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnInClass.Click
        Dim totalRevenues As Double
        Dim highestSales As Integer = -1
        Dim highestTitle As String
        Dim highestArtist As String

        Dim cnt As Integer
        For cnt = 0 To numCD - 1
            totalRevenues = totalRevenues + CDs(cnt).revenues

            If CDs(cnt).sold >= highestSales Then
                ' we have a new highest seller
                highestSales = CDs(cnt).sold
                highestTitle = CDs(cnt).title
                highestArtist = CDs(cnt).artist

            Else


            End If

        Next cnt
        TxtRev.Text = totalRevenues.ToString("c")
        TxtTop.Text = highestTitle
        TxtTopArtist.Text = highestArtist

    End Sub
End Class