Can't get MSDN's example for Listbox to work

  • Thread starter Thread starter fiaolle
  • Start date Start date
F

fiaolle

Hi

I Can't get the MSDN's example for Listbox to work.The example is below. I
get an error in Listbox's sub ListBox1_SelectedValueChanged at row
textBox1.Text = ListBox1.SelectedValue and it happens after the line
ListBox1.ValueMember = "ShortName" is run. The error says Cast from type
'USState' to type 'String' is not valid.
I don't know why the code doesn't work, can anyone please explain that for
me.

Thank's
Fia


Public Class Form1
Inherits System.Windows.Forms.Form
Public Class USState
Private myShortName As String
Private myLongName As String
Public Sub New(ByVal strlongName As String, ByVal strShortName As String)
MyBase.New()
Me.myShortName = strShortName
Me.myLongName = strLongName
End Sub
Public ReadOnly Property ShortName() As String
Get
Return myShortName
End Get
End Property
Public ReadOnly Property LongName() As String
Get
Return myLongName
End Get
End Property
Public Overrides Function ToString() As String
Return Me.ShortName & " - " & Me.LongName
End Function
End Class
Public Class ListBoxSample3
Inherits Form
Friend WithEvents ListBox1 As ListBox = New ListBox
Dim textBox1 As TextBox = New TextBox
<System.STAThreadAttribute()> _
Public Shared Sub Main()
System.Windows.Forms.Application.Run(New ListBoxSample3)
End Sub
Public Sub New()
Me.AutoScaleBaseSize = New Size(5, 13)
Me.ClientSize = New Size(292, 181)
Me.Text = "ListBox Sample3"
ListBox1.Location = New Point(24, 16)
ListBox1.Name = "ListBox1"
ListBox1.Size = New Size(232, 130)

textBox1.Location = New Point(24, 160)
textBox1.Name = "textBox1"
textBox1.Size = New Size(40, 24)
Me.Controls.AddRange(New Control() {ListBox1, textBox1})
' Populates the list box using DataSource.
' DisplayMember is used to display just the long name of each state.
Dim USStates As New ArrayList
USStates.Add(New USState("Washington", "WA"))
USStates.Add(New USState("West Virginia", "WV"))
USStates.Add(New USState("Wisconsin", "WI"))
USStates.Add(New USState("Wyoming", "WY"))
ListBox1.DataSource = USStates
ListBox1.DisplayMember = "LongName"
ListBox1.ValueMember = "ShortName"
End Sub
Private Sub InitializeComponent()
End Sub
Private Sub ListBox1_SelectedValueChanged(ByVal sender As System.Object,
ByVal e As System.EventArgs) Handles ListBox1.SelectedValueChanged
If ListBox1.SelectedIndex <> -1 Then
textBox1.Text = ListBox1.SelectedValue
End If
End Sub
End Class
End Class
 
Looks like the sample is broken. Change this:

Private Sub ListBox1_SelectedValueChanged(ByVal sender As System.Object,
ByVal e As System.EventArgs) Handles ListBox1.SelectedValueChanged
If ListBox1.SelectedIndex <> -1 Then
textBox1.Text = ListBox1.SelectedValue
End If
End Sub

to this:

Private Sub ListBox1_SelectedValueChanged(ByVal sender As System.Object,
ByVal e As System.EventArgs) Handles ListBox1.SelectedValueChanged
If ListBox1.SelectedIndex <> -1 Then
textBox1.Text = ListBox1.SelectedValue.ToString()
End If
End Sub

/claes
 
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