CODEWITHSUNDEEP
vb.netfor-loopenumeration
MrDuckBringer
MrDuckBringer

Reputation: 55

List that this enumerator is bound to has been modified

I have this bit of code here, and at the next statement it's giving me an error saying:

List that this enumerator is bound to has been modified. An enumerator can only be used if the list does not change.

I really don't know how to further explain this issue, but if you need me to I can try.

For Each itemChecked In storedAuthorsListbox.CheckedItems
  Dim selectedAuthor As String = storedAuthorsListbox.SelectedItem.ToString()
  Dim authorFile As String = "Authors\" & itemChecked.ToString()
  Dim document As XmlReader = New XmlTextReader(authorFile)

  metaInfo &= "[Author]" & vbNewLine

  While (document.Read())
    Dim type = document.NodeType
    If (type = XmlNodeType.Element) Then
      If (document.Name = "Name") Then
        metaInfo &= "Name=" & document.ReadInnerXml.ToString() & vbNewLine
      ElseIf (document.Name = "Website") Then
        metaInfo &= "Website=" & document.ReadInnerXml.ToString() & vbNewLine
      ElseIf (document.Name = "Notes") Then
        metaInfo &= "Notes=" & document.ReadInnerXml.ToString() & vbNewLine
      End If
    End If
  End While
  document.Close()
Next

Upvotes: 2

Views: 4197

Answers (1)

Hans Passant
Hans Passant

Reputation: 942119

Some code somewhere is changing storedAuthorsListbox while you are iterating it. That code is not visible in the snippet. Do make sure that the posted code is not running in a worker thread, that is not legal. It certainly quacks like the kind of code you'd run in a worker.

The generic solution is to make a copy of the items and work from that copy instead of the control:

    Dim copy = storedAuthorsListBox.SelectedItems.OfType(Of String)().ToList()
    For Each itemchecked In copy
        '' etc..
    Next

If this runs in a worker thread then pass the copy to the worker.

Upvotes: 5

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