Populating checkbox list

Question

User237232814 posted

Hi! I'm really new in .Net and what I'm trying to do is the following.

I have a textbox control with a button then underneath of it a have a checkboxlist control and another button. Basically what I want to do is when a User enters something on the textbox and then press the Add button the text they enter gets added to the checkbox list. This I was able to do with no problems, The problems comes when I try to remove the selected Items on the checkbox list. I have the following code.

Protected Sub btnAdd_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnAdd.Click
        Dim myPhoneNumber As String = txtPhoneNumber.Text
        Dim myListOfPhoneNumbers As CheckBoxList = CType(chkPhoneNumbers, CheckBoxList)
        chkPhoneNumbers.Items.Add(Convert.ToString(myPhoneNumber))

        txtPhoneNumber.Text = Nothing
End Sub

Protected Sub btnDelete_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnDelete.Click
        Dim myListOfPhoneNumbers As CheckBoxList = CType(chkPhoneNumbers, CheckBoxList)

        chkPhoneNumbers.Items.Remove(chkPhoneNumbers.SelectedValue)

End Sub

The problem with the btnDelete_Click code is that If a select several items on the checkboxlist control only one of them gets removed. I tried this: but I get an error

Protected Sub btnDelete_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnDelete.Click
        Dim myListOfPhoneNumbers As CheckBoxList = CType(chkPhoneNumbers, CheckBoxList)

        For Each Item As ListItem In chkPhoneNumbers.Items
            If Item.Selected Then
                chkPhoneNumbers.Items.Remove(chkPhoneNumbers.SelectedValue)
            End If
        Next

End Sub

Any help would greatly be appreciated

Answer 1

User-925904572 posted

Hi,

 

From your code, results are as expeted. You pass the same value in your remove function, even though you loop.

Your second function should work once you have the proper types plugged in.

01.Protected Sub btnDelete_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnDelete.Click   
02.        Dim myListOfPhoneNumbers As CheckBoxList = CType(chkPhoneNumbers, CheckBoxList)   
03.  
04.        For Each Item As ListItem In chkPhoneNumbers.Items   
05.            If Item.Selected Then  
06.                chkPhoneNumbers.Items.Remove(chkPhoneNumbers.SelectedValue)    ' <<== even though you are looping, you are always passing the same value

                     chkPhoneNumbers.Items.Remove(Item)  ' <<== this should work

                     chkPhoneNumbers.Items.Remove(Item.Text)  '' << == this should also work

                     chkPhoneNumbers.Items.Remove(Item.Value) '' <<== this will work only if you assign a value to the item when adding....currently, you only add the text
07.            End If  
08.        Next  
09.  
10.End Sub 

Please mark as answered if this post has helped you

 

 

 

Answer 2

User237232814 posted

dzieba thanks for you reply, however I tried what you instructed and I get the following error:

Collection was modified; enumeration operation may not execute.

The line number is on the Next command. 

Thanks again

Carlos

Answer 3

User-952121411 posted

Yes the idea was correct, but the implementation was a bit off.  You will not be able to modify the collection in a For Each loop like that because the enumeration of items changed.  A solution is to loop from the end to the beginning.  Look at the code sample given in the following link:

Collection was modified; enumeration operation may not execute:

http://www.vbdotnetforums.com/vb-net-general-discussion/3833-collection-modified-enumeration-operation-may-not-execute.html

The code will probably change to something like this:

For i As Integer = (chkPhoneNumbers.Items.Count - 1) To 0 Step -1
    If chkPhoneNumbers.Items(i).Selected Then     
        chkPhoneNumbers.Items.RemoveAt(i)
    End If
Next

 

Answer 4

User237232814 posted

Thanks a lot it worked...