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

microsoft.public.dotnet.languages.vb

5 Jul 2006 8:56 PM

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

6 Jul 2006 2:28 PM

Claes Bergefall

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

Show quoteHide quote

"fiaolle" <fiao***@telia.com> wrote in message
news:XHVqg.7858$E02.2355@newsb.telia.net...
> 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
>
>