这个枚举器绑定的列表已被修改 [英] List that this enumerator is bound to has been modified

问题描述

我在这里有一些代码，在下一个语句中给我一个错误：
$ b

列举这个枚举器是必然会被修改。一个枚举器只能用在列表没有改变的情况下。

我真的不知道如何进一步解释这个问题，如果你需要我，我可以尝试。

 对于每个itemChecked在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 
 $ b while（document.Read（））
 Dim type = document.NodeType 
 If（type = XmlNodeType.Element）Then 
 If（document.Name = Name）然后
 metaInfo& =Name =& document.ReadInnerXml.ToString（）& vbNewLine 
 ElseIf（document.Name =Website）然后
 metaInfo& =Website =& document.ReadInnerXml.ToString（）& vbNewLine 
 ElseIf（document.Name =Notes）然后
 metaInfo& =Notes =& document.ReadInnerXml.ToString（）& vbNewLine 
 End If 
 End If 
 End While 
 document.Close（）
 Next 
  

解决方案

有些代码在迭代时正在改变storedAuthorsListbox。该代码在代码片段中不可见。确保发布的代码不在工作线程中运行，这是不合法的。它肯定是呱呱叫，就像你在工作人员中运行的那种代码一样。

通用的解决方案是复制这些项目，控制：
$ b $ pre $ Dim copy = storedAuthorsListBox.SelectedItems.OfType（Of String）（）。ToList（）
For Each itemchecked在复制
等等。
下一个


一个工作线程然后将副本传递给工作人员。

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

解决方案

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.

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