原文： http://zetcode.com/gui/vbwinforms/controls/

Visual Basic Winforms 编程教程的这一部分将介绍基本控件。

Winforms 控件是应用的基本构建块。 Winforms 具有广泛的各种控件。 按钮，复选框，滑块，列表框等。程序员完成工作所需的一切。 在本教程的这一部分中，我们将描述几个有用的控件。

Label

Label是用于显示文本或图像的简单控件。 它没有得到关注。

  1. ' ZetCode Mono Visual Basic Winforms tutorial
  2. '
  3. ' This program shows lyrics of a song
  4. '
  5. ' author jan bodnar
  6. ' last modified May 2009
  7. ' website www.zetcode.com
  9. Imports System.Windows.Forms
  10. Imports System.Drawing
  12. Public Class WinVBApp
  13.     Inherits Form
  15.     Dim lyrics As String = "Meet you downstairs in the bar and heard" & vbNewLine & _
  16. "your rolled up sleeves and your skull t-shirt" & vbNewLine & _
  17. "You say why did you do it with him today?" & vbNewLine & _
  18. "and sniff me out like I was Tanqueray" & vbNewLine & _
  19. "" & vbNewLine & _
  20. "cause you're my fella, my guy" & vbNewLine & _
  21. "hand me your stella and fly" & vbNewLine & _
  22. "by the time I'm out the door" & vbNewLine & _
  23. "you tear men down like Roger Moore" & vbNewLine & _
  24. "" & vbNewLine & _
  25. "I cheated myself" & vbNewLine & _
  26. "like I knew I would" & vbNewLine & _
  27. "I told ya, I was trouble" & vbNewLine & _
  28. "you know that I'm no good"
  30.     Public Sub New()
  32.        Me.Text = "You know I'm no Good"
  33.        Me.Size = New Size(300, 250)
  35.        Me.InitUI
  37.        Me.CenterToScreen
  39.     End Sub
  41.     Private Sub InitUI
  43.         Dim font As New Font("Serif", 10)
  45.         Dim label As New Label
  46.         label.Parent = Me
  47.         label.Text = lyrics
  48.         label.Font = font
  49.         label.Location = New Point(10, 10)
  50.         label.Size = New Size (290, 290)
  52.     End Sub
  54.     Public Shared Sub Main
  55.         Application.Run(New WinVBApp)
  56.     End Sub
  58. End Class

在我们的示例中，我们在标签控件中显示歌曲的歌词。

  1.  Dim lyrics As String = "Meet you downstairs in the bar and heard" & vbNewLine & _
  2. "your rolled up sleeves and your skull t-shirt" & vbNewLine & _ 
  3. ...

我们定义了多行文字。 与 C# ，Python 或 Ruby 不同，没有简单的结构可以用 Visual Basic 语言创建多行文本。 若要在 Visual Basic 中创建多行文本，我们使用vbNewLine打印常量，+连接字符和_行终止字符。

  1. Dim label As New Label

Label控件已创建。

  1. label.Text = lyrics

我们为标签设置文本。

  1. Dim font As New Font("Serif", 10)
  2. ...
  3. label.Font = font

标签文本的字体设置为 Serif，10px。

基本控制 - 图1

图：Label

CheckBox

CheckBox是具有两个状态的控件：开和关。 它是带有标签或图像的盒子。 如果选中了CheckBox，则在方框中用勾号表示。 CheckBox可用于在启动时显示/隐藏启动屏幕，切换工具栏的可见性等。

  1. ' ZetCode Mono Visual Basic Winforms tutorial
  2. '
  3. ' This program toggles the title of the
  4. ' window with the CheckBox control
  5. '
  6. ' author jan bodnar
  7. ' last modified May 2009
  8. ' website www.zetcode.com
  10. Imports System.Windows.Forms
  11. Imports System.Drawing
  13. Public Class WinVBApp
  14.     Inherits Form
  16.     Public Sub New
  18.        Me.Text = "CheckBox"
  19.        Me.Size = New Size(220, 170)
  21.        Me.InitUI
  23.        Me.CenterToScreen
  25.     End Sub
  27.     Private Sub InitUI
  29.         Dim cb As New CheckBox
  30.         cb.Parent = Me
  31.         cb.Location = New Point(30, 30)
  32.         cb.Text = "Show Title"
  33.         cb.Checked = True
  35.         AddHandler cb.CheckedChanged, AddressOf Me.OnChanged
  37.     End Sub
  39.     Private Sub OnChanged(ByVal sender As Object, ByVal e As EventArgs)
  41.         If sender.Checked
  42.             Text = "CheckBox"
  43.         Else 
  44.             Text = ""
  45.         End If
  47.     End Sub
  49.     Public Shared Sub Main
  50.         Application.Run(New WinVBApp)
  51.     End Sub
  53. End Class

我们的代码示例根据窗口的状态显示或隐藏窗口的标题。

  1. Dim cb As New CheckBox

CheckBox控件已创建。

  1. cb.Text = "Show Title"
  2. cb.Checked = True

当应用启动时，我们显示标题。 然后将CheckBox控件设置为选中状态。

  1. AddHandler cb.CheckedChanged, AddressOf Me.OnChanged

当我们单击CheckBox控件时，将触发CheckedChanged事件。 我们用OnChanged方法对这个特定事件做出反应。

  1. If sender.Checked
  2.     Text = "CheckBox"
  3. Else 
  4.     Text = ""
  5. End If

在这里，我们切换窗口的标题。

基本控制 - 图2

图：CheckBox

ComboBox

ComboBox是一个组合了按钮或可编辑字段和下拉列表的控件。 用户可以从下拉列表中选择一个值，该列表应用户的要求出现。 如果使组合框可编辑，则组合框将包含一个可编辑字段，用户可以在其中输入值。

  1. ' ZetCode Mono Visual Basic Winforms tutorial
  2. '
  3. ' In this program, we use the ComboBox
  4. ' control to select an option. 
  5. ' The selected option is shown in the
  6. ' Label component.
  7. '
  8. ' author jan bodnar
  9. ' last modified May 2009
  10. ' website www.zetcode.com
  12. Imports System.Windows.Forms
  13. Imports System.Drawing
  15. Public Class WinVBApp
  16.     Inherits Form
  18.     Private Dim label As Label
  20.     Public Sub New
  22.        Me.Text = "ComboBox"
  23.        Me.Size = New Size(240, 240)
  25.        Me.InitUI
  27.        Me.CenterToScreen
  29.     End Sub
  31.     Private Sub InitUI
  33.         Dim cb As New ComboBox
  34.         cb.Parent = Me
  35.         cb.Location = New Point(50, 30)
  37.         cb.Items.AddRange(New Object() {"Ubuntu", _
  38.             "Mandriva", _
  39.             "Red Hat", _
  40.             "Fedora", _
  41.             "Gentoo"}) 
  43.         label = New Label
  44.         label.Location = New Point(50, 140)
  45.         label.Parent = Me
  46.         label.Text = "..."
  48.         AddHandler cb.SelectionChangeCommitted, AddressOf Me.OnChanged
  50.     End Sub
  52.     Private Sub OnChanged(ByVal sender As Object, ByVal e As EventArgs)
  54.         label.Text = sender.Text
  56.     End Sub
  58.     Public Shared Sub Main
  59.         Application.Run(New WinVBApp)
  60.     End Sub
  62. End Class

我们的代码编程示例显示了一个包含五个项目的组合框。 所选项目显示在标签控件中。

  1. Dim cb As New ComboBox

ComboBox控件已创建。

  1. cb.Items.AddRange(New Object() {"Ubuntu", _
  2.     "Mandriva", _
  3.     "Red Hat", _
  4.     "Fedora", _
  5.     "Gentoo"})

ComboBox控件中充满了项目。

  1. AddHandler cb.SelectionChangeCommitted, AddressOf Me.OnChanged

如果我们从组合框中选择一个项目，则会触发SelectionChangeCommitted事件。

  1. Private Sub OnChanged(ByVal sender As Object, ByVal e As EventArgs)
  3.     label.Text = sender.Text
  5. End Sub

在这里，将从组合框中选择的文本复制到标签。

基本控制 - 图3

图：ComboBox

MonthCalendar

在下一个示例中，我们将显示MonthCalendar控件。 MonthCalendar 控件允许用户使用视觉显示选择日期。

  1. ' ZetCode Mono Visual Basic Winforms tutorial
  2. '
  3. ' In this program, we use the MonthCalendar
  4. ' control to select a date.
  5. ' The selected date is shown in the
  6. ' Label control.
  7. '
  8. ' author jan bodnar
  9. ' last modified May 2009
  10. ' website www.zetcode.com
  12. Imports System.Windows.Forms
  13. Imports System.Drawing
  15. Public Class WinVBApp
  16.     Inherits Form
  18.     Private Dim label As Label
  20.     Public Sub New
  22.        Me.Text = "MonthCalendar"
  23.        Me.Size = New Size(240, 240)
  25.        Me.InitUI
  27.        Me.CenterToScreen
  29.     End Sub
  31.     Private Sub InitUI
  33.         Dim calendar As New MonthCalendar
  34.         calendar.Parent = Me
  35.         calendar.Location = New Point(20, 20)
  37.         label = New Label
  38.         label.Location = New Point(40, 170)
  39.         label.Parent = Me
  40.         Dim dt As DateTime = calendar.SelectionStart
  41.         label.Text = dt.Month & "/" & dt.Day & "/" & dt.Year
  43.         AddHandler calendar.DateSelected, AddressOf Me.OnSel
  45.     End Sub
  47.     Private Sub OnSel(ByVal sender As Object, ByVal e As DateRangeEventArgs)
  49.         Dim dt As DateTime = sender.SelectionStart
  50.         label.Text = dt.Month & "/" & dt.Day & "/" & dt.Year
  52.     End Sub
  54.     Public Shared Sub Main
  55.         Application.Run(New WinVBApp)
  56.     End Sub
  58. End Class

在示例中，我们显示了MonthCalendar和Label。 后者显示当前选择的日期。

  1. Private Sub OnSel(ByVal sender As Object, ByVal e As DateRangeEventArgs)
  3.     Dim dt As DateTime = sender.SelectionStart
  4.     label.Text = dt.Month & "/" & dt.Day & "/" & dt.Year
  6. End Sub

当我们从MonthCalendar中选择一个日期时，就会调用OnSel方法。 SelectionStart属性获取所选日期范围的开始日期。

基本控制 - 图4

图：MonthCalendar

TextBox

TextBox控件用于显示或接受某些文本。 文本可以是单行或多行。 此控件还可以进行密码屏蔽。

  1. ' ZetCode Mono Visual Basic Winforms tutorial
  2. '
  3. ' This program demonstrates the 
  4. ' TextBox control. Text entered in the TextBox
  5. ' control is shown in a Label control.
  6. '
  7. ' author jan bodnar
  8. ' last modified May 2009
  9. ' website www.zetcode.com
  11. Imports System.Windows.Forms
  12. Imports System.Drawing
  14. Public Class WinVBApp
  15.     Inherits Form
  17.     Private Dim label As Label
  19.     Public Sub New
  21.        Me.Text = "TextBox"
  22.        Me.Size = New Size(250, 200)
  24.        Me.InitUI
  26.        Me.CenterToScreen
  28.     End Sub
  30.     Private Sub InitUI
  32.         label = New Label
  33.         label.Parent = Me
  34.         label.Text = "..."
  35.         label.Location = New Point(60, 40)
  36.         label.AutoSize = True
  38.         Dim tbox As New TextBox
  39.         tbox.Parent = Me
  40.         tbox.Location = New Point(60, 100)
  42.         AddHandler tbox.KeyUp, AddressOf Me.OnKeyUp
  44.     End Sub
  46.     Private Sub OnKeyUp(ByVal sender As Object, ByVal e As KeyEventArgs)
  48.         Me.label.Text = sender.Text
  50.     End Sub
  52.     Public Shared Sub Main
  53.         Application.Run(New WinVBApp)
  54.     End Sub
  56. End Class

本示例显示一个文本框和一个标签。 我们在文本框中键入的文本将立即显示在标签控件中。

  1. label = New Label
  2. ...
  3. label.AutoSize = True

Label控件已创建。 AutoSize属性确保Label增长以显示文本。

  1. Dim tbox As New TextBox
  2. ...
  3. AddHandler tbox.KeyUp, AddressOf Me.OnKeyUp

我们插入KeyUp事件。 释放按键时，将调用OnKeyUp方法。

  1. Private Sub OnKeyUp(ByVal sender As Object, ByVal e As KeyEventArgs)
  3.     Me.label.Text = sender.Text
  5. End Sub

在OnKeyUp方法中，我们使用文本框控件中的文本更新了标签控件。

基本控制 - 图5

图：TextBox

我们已经完成了 Visual Basic Winforms 教程的这一章，专门讨论基本控件。