Question

Listbox woes - cannot remove or disable databound selected item in listbox

Asked by: Strongs

Hi everyone,

I have a win form with listboxes. One listbox is bound to a dataset and I want the user to select an item from this listbox, click on a button and the item is moved to the other listbox. This part I have got to work. What i cannot seem to fathom out is how to remove or disable the selected item from the databound listbox, so that the user cannot reselect the item. Currently the user can select one item and populate the other listbox with duplicates ad infinitum.

I also need to allow the user to go the other way, that is, any items they choose to remove from the listbox that has been populated with selected items from the databound listbox, they can do so and that item is added back to the databound listbox.

After searching the net, i tried the code pasted below, but this simply removes ALL records from the databound listbox.

Hope someone can help.

Private Sub btnMoveRight_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnMoveRight.Click
        Dim tmpstr As DataRowView 
        Try
            If lbAvailQuestions.SelectedIndex = -1 Then
                Exit Sub
            Else
                tmpstr = CType(Me.lbAvailQuestions.SelectedItem, DataRowView)
                Me.lbChosenQuest.Items.Add(tmpstr("QuestText"))
                Me.lbAvailQuestions.DataSource = Nothing 'this deletes all items in the listbox
                Me.lbAvailQuestions.Refresh()
                Me.lbAvailQuestions.Items.RemoveAt(lbAvailQuestions.SelectedIndex) 'this throws an error because the list no longer exists
            End If
        Catch ex As Exception
            MessageBox.Show(Err.Number & vbNewLine & ex.Message, "Data Error", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
        End Try 
    End Sub

                                  
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Asked On
2009-11-07 at 06:21:10ID24880418
Tags

Visual Studio 2008

,

vb.net

,

visual basic

Topics

Microsoft Visual Basic.Net

,

Visual Studio

Participating Experts
2
Points
500
Comments
7

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Answers

 

by: Ashok9Posted on 2009-11-07 at 06:33:53ID: 25766441

Actually that you can not do if the listbox is bound to any dataset.

So you have to use temporary hidden listbox or collection for the dataset.
From that temporary listbox you have to populate your main list box.

 

by: StrongsPosted on 2009-11-07 at 07:04:49ID: 25766527

Hi Ashok,

thanks for responding so quickly.
Judging by the other posts I have been trawling on this subject, i suspected this may be the case.

Could you please give me an example of how you would go about this? The items that the user selects, will be used in an SQL query to generate a question paper.

many thanks

 

by: Ashok9Posted on 2009-11-07 at 07:39:14ID: 25766617

make that listbox invisible.

Also create a new listbox for availableQuestions.
That will be populated from temporary list box and on top of it will remove already selected items.

I think this will solve your purpose.

 

by: StrongsPosted on 2009-11-07 at 08:57:17ID: 25767055

Hi Ashok,

thanks for the tip. The form has several one to many relationships attached to the listboxes.
I set the bound listbox visible property to false (lbAvailQuestions). I am now trying to populate the temporary listbox (lbPopWithAvailQ) with the values from the hidden listbox when the user clicks on the listbox where the relationship PK/FK corresponds to the hidden listbox. I have fired this event in the SelectedValueChanged.

It seems to be working, but i just get one record duplicated to the value of the records contained in the relationship.

I have attached the code snippet for the event and would be grateful if you could try to see where i am going wrong.

Many thanks.

Private Sub lbTrgObj_SelectedValueChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles lbTrgObj.SelectedValueChanged
        Dim rwText As DataRowView
        Dim i As Integer 
        Me.lbPopWithAvailQ.Items.Clear() 
        For i = 1 To Me.lbAvailQuestions.Items.Count
            rwText = CType(Me.lbAvailQuestions.SelectedItem, DataRowView)
            Me.lbPopWithAvailQ.Items.Add(rwText("QuestText"))
        Next
    End Sub

                                              
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by: CodeCruiserPosted on 2009-11-07 at 11:07:27ID: 25767604

Change this
For i = 1 To Me.lbAvailQuestions.Items.Count

to
For i = 0 To Me.lbAvailQuestions.Items.Count - 1

 

by: StrongsPosted on 2009-11-08 at 23:09:14ID: 25773865

Hi CodeCruiser/Ashok,

thank you for posting a solution. Got this to work with the code below based on your suggestion.

Unfortunately my idea was to create an SQL statement based on the questions selected. This is proving difficult and I will probably need to get the QuestionID (pk) rather than the Question Text.

I need to think my strategy again. I will have to eliminate the TrgObj ListBox which is the one to many datatable from the bound datatset for the questions and bind all questions programmatically. Fom there I will have to somehow pick up the QuestionID.

I may have to re-post for another solution on this one.

Thanks to both of you for your valued help.

Private Sub lbTrgObj_SelectedValueChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles lbTrgObj.SelectedValueChanged
        Dim rwText As DataRowView
        Dim chTxt As String 
        Try
            'clear the listbox ready for re-population
            Me.lbPopWithAvailQ.Items.Clear() 
            'populate the listbox
            For i As Integer = 0 To Me.lbAvailQuestions.Items.Count - 1
                rwText = CType(Me.lbAvailQuestions.Items(i), DataRowView)
                Me.lbPopWithAvailQ.Items.Add(rwText("QuestText"))
            Next 
            'if an item exists in the lbChosenQuest listbox, then
            'delete it from the lbPopWithAvailQ listbox
            For j As Integer = 0 To Me.lbChosenQuest.Items.Count - 1
                chTxt = Me.lbChosenQuest.Items(j).ToString
                If Me.lbPopWithAvailQ.Items.Contains(chTxt) Then
                    Me.lbPopWithAvailQ.Items.Remove(chTxt)
                End If
            Next
        Catch ex As Exception
            MessageBox.Show(Err.Number & vbNewLine & ex.Message, "Data Error", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
        End Try 
    End Sub

                                              
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by: StrongsPosted on 2009-11-09 at 07:57:57ID: 31651383

Thank you both for your input to this solution.

20120131-EE-VQP-002

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