MAIN MENU Public Class frmMainMenu Private Sub btnAddBooks_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAddBooks.Click Me.Hide() Dim frmAddBooksGUI = New frmAddBooks() frmAddBooksGUI.ShowDialog() Me.Show() End Sub Private Sub btnUpdateBooks_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnUpdateBooks.Click Me.Hide() Dim frmUpdateBooksGUI = New frmUpdateBooks() frmUpdateBooksGUI.ShowDialog() Me.Show() End Sub Private Sub frmDeleteBooks_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles frmDeleteBooks.Click Me.Hide() Dim frmDeleteBooksGUI = New frmDeleteBooks() frmDeleteBooksGUI.ShowDialog() Me.Show() End Sub Private Sub btnExit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnExit.Click clsBook.Terminate() Me.Close() End Sub Private Sub frmMainMenu_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load clsBook.Initialize() End Sub Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Quit.Click End Sub
End Class

UPDATE BOOKS
Public Class frmUpdateBooks Private books As New ArrayList Private index As Integer = 0 Private Sub ShowCurrentRecord() Dim PurchasePrice, SalePrice As Decimal If books.Count > 0 Then txtBookID.Text = books(index).BookID txtAuthor.Text = books(index).Author txtTitle.Text = books(index).Title PurchasePrice = books(index).PurchasePrice txtPurchasePrice.Text = PurchasePrice.ToString("N") SalePrice = books(index).SalePrice txtSalePrice.Text = SalePrice.ToString("N") txtInventory.Text = books(index).Inventory End If End Sub Private Sub btnUpdate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnUpdate.Click If books.Count > 0 Then Dim aBook As New clsBook(txtBookID.Text, txtAuthor.Text, _ txtTitle.Text, CDec(txtPurchasePrice.Text), _ CDec(txtSalePrice.Text), CInt(txtInventory.Text)) aBook.Update() books(index) = aBook MessageBox.Show("Record has been updated in the database.") End If End Sub Private Sub btnMoveFirst_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnMoveFirst.Click index = 0 Me.ShowCurrentRecord() End Sub Private Sub btnMovePrevious_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnMovePrevious.Click If index > 0 Then index = index - 1 Me.ShowCurrentRecord() End If End Sub Private Sub btnMoveNext_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnMoveNext.Click If index < (books.Count - 1) Then index = index + 1 Me.ShowCurrentRecord() End If End Sub Private Sub btnMoveLast_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnMoveLast.Click If books.Count > 0 Then index = books.Count - 1 Me.ShowCurrentRecord() End If End Sub Private Sub btnClose_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClose.Click Me.Close() End Sub Private Sub frmUpdateBooks_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Me.Load books = clsBook.GetAll() If books.Count = 0 Then MessageBox.Show("There are no records in the database.") Me.Close() Else lblNumberRecords.Text = books.Count Me.ShowCurrentRecord() End If End Sub End Class DELETE BOOKS Public Class frmDeleteBooks Private books As New ArrayList Private index As Integer = 0 Private Sub ShowCurrentRecord() Dim PurchasePrice, SalePrice As Decimal If books.Count > 0 Then txtBookID.Text = books(index).BookID txtAuthor.Text = books(index).Author txtTitle.Text = books(index).Title PurchasePrice = books(index).PurchasePrice txtPurchasePrice.Text = PurchasePrice.ToString("N") SalePrice = books(index).SalePrice txtSalePrice.Text = SalePrice.ToString("N") txtInventory.Text = books(index).Inventory Else txtBookID.Text = "" txtAuthor.Text = "" txtTitle.Text = "" txtPurchasePrice.Text = "" txtSalePrice.Text = "" txtInventory.Text = "" End If End Sub Private Sub btnDelete_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDelete.Click If books.Count > 0 Then Dim aBook As New clsBook(txtBookID.Text, txtAuthor.Text, _ txtTitle.Text, CDec(txtPurchasePrice.Text), _ CDec(txtSalePrice.Text), CInt(txtInventory.Text)) aBook.Delete() books.RemoveAt(index) lblNumberRecords.Text = books.Count If index = books.Count Then index = index - 1 Me.ShowCurrentRecord() MessageBox.Show("Record has been deleted from the database.") Else MessageBox.Show("There are no more records in the database.") End If End Sub Private Sub btnMoveFirst_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnMoveFirst.Click index = 0 Me.ShowCurrentRecord() End Sub Private Sub btnMovePrevious_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnMovePrevious.Click If index > 0 Then index = index - 1 Me.ShowCurrentRecord() End If End Sub Private Sub btnMoveNext_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnMoveNext.Click If index < (books.Count - 1) Then index = index + 1 Me.ShowCurrentRecord() End If End Sub Private Sub btnMoveLast_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnMoveLast.Click If books.Count > 0 Then index = books.Count - 1 Me.ShowCurrentRecord() End If End Sub Private Sub btnClose_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClose.Click Me.Close() End Sub Private Sub frmDeleteBooks_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load books = clsBook.GetAll() If books.Count = 0 Then MessageBox.Show("There are no records in the database.") Me.Close() Else lblNumberRecords.Text = books.Count Me.ShowCurrentRecord() End If End Sub
End Class ADD BOOKS
Public Class frmAddBooks Private books As New ArrayList Private Sub btnAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAdd.Click If txtBookID.Text.Length = 0 Or txtAuthor.Text.Length = 0 Or _ txtTitle.Text.Length = 0 Or txtPurchasePrice.Text.Length = 0 Or _ txtSalePrice.Text.Length = 0 Or txtInventory.Text.Length = 0 Then MessageBox.Show("Please enter all the data.") ElseIf Not IsValidISBN(txtBookID.Text) Then MessageBox.Show("Invalid ISBN. Please enter a valid ISBN.") txtBookID.Focus() ElseIf Not IsNumeric(txtPurchasePrice.Text) Then MessageBox.Show("Please enter a numeric Purchase Price.") txtPurchasePrice.Focus() ElseIf Not IsNumeric(txtSalePrice.Text) Then MessageBox.Show("Please enter a numeric Sale Price.") txtSalePrice.Focus() ElseIf Not IsNumeric(txtInventory.Text) Then MessageBox.Show("Please enter a numeric Number of Items on Stock.") txtInventory.Focus() Else Dim aBook As New clsBook(txtBookID.Text, txtAuthor.Text, _ txtTitle.Text, CDec(txtPurchasePrice.Text), CDec(txtSalePrice.Text), _ CInt(txtInventory.Text)) Try aBook.Add() books.Add(aBook) lblNumberRecords.Text = books.Count MessageBox.Show("Record added to the database.") btnClear.PerformClick() Catch MessageBox.Show("A book with ISBN = " & txtBookID.Text & _ " already exists in the database." & vbCrLf & _ "Please enter a new ISBN or Press Clear to enter details of a new book.") txtBookID.Focus() End Try End If End Sub Private Sub btnClear_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClear.Click txtBookID.Text = "" txtAuthor.Text = "" txtTitle.Text = "" txtPurchasePrice.Text = "" txtSalePrice.Text = "" txtInventory.Text = "" txtBookID.Focus() End Sub Private Sub btnClose_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClose.Click Me.Close() End Sub Private Function IsValidISBN(ByVal ISBN As String) As Boolean If ISBN.Length = 10 Then Return IsValidISBN10(ISBN) Else Return IsValidISBN13(ISBN) End Function Private Function IsValidISBN10(ByVal ISBN As String) As Boolean Dim i, sum, cd As Integer Dim checkDigit As Char For i = 0 To ISBN.Length - 2 sum = sum + Val(ISBN.Chars(i)) * (10 - i) Next cd = (11 - sum Mod 11) Mod 11 If cd = 10 Then checkDigit = "X" Else checkDigit = cd.ToString() If checkDigit = ISBN.Chars(i) Then Return True Else Return False End Function Private Function IsValidISBN13(ByVal ISBN As String) As Boolean Dim i, sum, cd As Integer Dim checkDigit As Char For i = 0 To 10 Step 2 sum = sum + Val(ISBN.Chars(i)) sum = sum + Val(ISBN.Chars(i + 1)) * 3 Next cd = (10 - sum Mod 10) Mod 10 checkDigit = cd.ToString() If checkDigit = ISBN.Chars(i) Then Return True Else Return False End Function Private Sub frmAddBooks_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load books = clsBook.GetAll() lblNumberRecords.Text = books.Count End Sub
End Class