Visual Basic.NET How to Program (PDF)

1008 ASP .NET, Web Forms and Web Controls Chapter 20
17 Public Class Login
18 Inherits System.Web.UI.Page
19
20 Protected WithEvents requiredPasswordValidator As _
21 RequiredFieldValidator
22
23 Protected WithEvents invalidPasswordValidator As _
24 CustomValidator
25
26 Protected WithEvents submitButton As Button
27 Protected WithEvents passwordTextBox As TextBox
28 Protected WithEvents passwordLabel As Label
29 Protected WithEvents nameList As DropDownList
30 Protected WithEvents nameLabel As Label
31 Protected WithEvents OleDbDataAdapter1 As OleDbDataAdapter
32 Protected WithEvents OleDbSelectCommand1 As OleDbCommand
33 Protected WithEvents OleDbInsertCommand1 As OleDbCommand
34 Protected WithEvents OleDbUpdateCommand1 As OleDbCommand
35 Protected WithEvents OleDbDeleteCommand1 As OleDbCommand
36 Protected WithEvents OleDbConnection1 As OleDbConnection
37 Protected WithEvents promptLabel As Label
38 Protected dataReader As OleDbDataReader
39
40 ' Visual Studio .NET generated code
41
42 Private Sub Page_Init(ByVal sender As System.Object, _
43 ByVal e As System.EventArgs) Handles MyBase.Init
44
45 InitializeComponent()
46
47 ' if page loads due to postback, process information
48 ' otherwise, page is loading for first time, so
49 ' do nothing
50 If Not IsPostBack Then
51
52 ' open database and read data
53 Try
54 ' open database connection
55 OleDbConnection1.Open()
56
57 ' execute query
58 dataReader = _
59 OleDbDataAdapter1.SelectCommand.ExecuteReader()
60
61 ' while we can read row from query result,
62 ' add first item to drop-down list
63 While (dataReader.Read())
64 nameList.Items.Add(dataReader.GetString(0))
65 End While
66
67 ' catch error if database cannot be opened
68 Catch exception As OleDbException
69 Response.Write("Unable to open database!")
Fig. 20.39 Code-behind file for the login page for authors application (part 2 of 5).