Private Sub showSelectedButton_Click(ByVal sender As Object, ByVal e As System.EventArgs)
    Dim selectedIndex As Integer
    selectedIndex = comboBox1.SelectedIndex
    Dim selectedItem As Object
    selectedItem = comboBox1.SelectedItem

    MessageBox.Show("Selected Item Text: " & selectedItem.ToString() & Microsoft.VisualBasic.Constants.vbCrLf & _
                        "Index: " & selectedIndex.ToString())
End Sub

' 导入命名空间
Imports System.Drawing
Imports System.Drawing.Drawing2D
Imports System.Windows.Forms

public class ComboBoxSelectionEventAddValue
   public Shared Sub Main
        Application.Run(New Form1)
   End Sub
End class

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 ComboBox1 As System.Windows.Forms.ComboBox
    Friend WithEvents TextBox1 As System.Windows.Forms.TextBox
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        Me.ComboBox1 = New System.Windows.Forms.ComboBox

        Me.TextBox1 = New System.Windows.Forms.TextBox
        Me.SuspendLayout()
        '
        'ComboBox1
        '
        Me.ComboBox1.Location = New System.Drawing.Point(72, 72)
        Me.ComboBox1.Name = "ComboBox1"
        Me.ComboBox1.Size = New System.Drawing.Size(121, 21)
        Me.ComboBox1.TabIndex = 0
        Me.ComboBox1.Text = "ComboBox1"

        '
        'TextBox1
        '
        Me.TextBox1.Location = New System.Drawing.Point(16, 168)
        Me.TextBox1.Name = "TextBox1"
        Me.TextBox1.Size = New System.Drawing.Size(256, 20)
        Me.TextBox1.TabIndex = 2
        Me.TextBox1.Text = ""
        '
        'Form1
        '
        Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
        Me.ClientSize = New System.Drawing.Size(292, 273)
        Me.Controls.Add(Me.TextBox1)
        Me.Controls.Add(Me.ComboBox1)
        Me.Name = "Form1"
        Me.Text = "Form1"
        Me.ResumeLayout(False)

    End Sub

#End Region

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        For i As Integer = 0 To 10
            ComboBox1.Items.Add("Item " + i.ToString())
        Next
        ComboBox1.Text = "Choose one..."
    End Sub

    Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
        Dim intSelectedIndex As Integer
        intSelectedIndex = ComboBox1.SelectedIndex
        Dim objSelectedItem As Object
        objSelectedItem = ComboBox1.SelectedItem

        TextBox1.Text = "Item's index: " & intSelectedIndex & _
        ". Item's text: " & objSelectedItem.ToString()
    End Sub
End Class