The element list has changed. The enumeration operation failed to continue.

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Hello,

I am trying to delete the child nodes of a node. During the execution of the foreach loop I am having an error- "The element list has changed. The enumeration operation failed to continue." I think because I am changing the XMLfile I am having that error but dont know how to fix it. Can someone correct my code?

MSIL

XmlDocument xmlDocument = new XmlDocument();
           xmlDocument.Load(@"C:\Users\Orcun Iyigun\Desktop\Projects\Rules.xml");

           XmlNodeList ratingNodes = xmlDocument.GetElementsByTagName("Rule/Rating");
           XmlNodeList mailtoNodes = xmlDocument.GetElementsByTagName("Rule/Mailto");
           XmlNodeList ruleNodes = xmlDocument.GetElementsByTagName("Rule");
           
           foreach (ListViewItem item in lvRules.Items)
           {
               if (item.Selected)
               {
                   string ratingVal = item.SubItems[0].Text;
                   string mailtoVal = item.SubItems[1].Text;
                   string ratmailNode = ratingVal + mailtoVal;


                   foreach (XmlNode deleteXMLnode in ruleNodes)
                   {
                       if (deleteXMLnode.InnerText == ratmailNode)
                       {
                           deleteXMLnode.ParentNode.RemoveChild(deleteXMLnode);
                       }
                   }
                   lvRules.Items.Remove(item);
               }
           }
           xmlDocument.Save(@"C:\Users\Orcun Iyigun\Desktop\Projects\Rules.xml");

Posted 2-Nov-10 14:56pm

Orcun Iyigun

Updated 19-Oct-20 0:01am

v2

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3 solutions

Solution 2

Your problem is that you are getting the ListViewItemCollection at the start of the foreach loop.
You need to get the ListViewItemsCollection before starting the loop.

C#

ListView.ListViewItemCollection lvIC = lvRules.Items;
foreach (ListViewItem item in lvIC)
{
    .
    .
    .
    lvRules.Items.Remove(item);
}

This is why when looping through item collections you don't make the call to get the collection a part of the loop.

For the second foreach loop you need to change how you get the rule nodes use SelectNodes with an XPath query instead like;

XmlNodeList ruleNodes = xmlDocument.SelectNodes("doc/Rule");

Posted 2-Nov-10 20:10pm

Rod Kemp

Updated 3-Nov-10 15:27pm

v4

Comments

Orcun Iyigun 3-Nov-10 11:44am

Still I am having the same error on the inner(second) foreach loop. I have changed the first foreach loop as you said but it is not working.

hatelove420 9-Feb-13 4:41am

i got the same problem can any one be clear to explain the above problem

Solution 3

Changing the selection from GetElementsByTagName to SelectNodes worked for me. Apparently the GetElementsByTagName method changes the result of the IEnumerable during the loop (if you debug, you'll see the count of items decrease) but the SelectNodes result stays the same.

private XmlDocument RemoveDrawingNodes(XmlDocument xmlDocument)
{
    var drawingNodes = xmlDocument.SelectNodes("//w:drawing", XmlNamespaceManager);

    foreach (XmlElement element in drawingNodes)
    {
        element.ParentNode.RemoveChild(element);
    }
    return xmlDocument;
}

Posted 19-Oct-20 0:02am

hilvarenbeek

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Nish Nishant · Accepted Answer · 2010-11-02T15:26:00

You can convert the foreach into a for loop, but even then every time you call RemoveChild, you must adjust the loop variable if you are using a cached length condition to exit the for loop.

Actually, even if you do not cache the for-condition, you still need to adjust the loop variable. For an example, see the code snippet below:

C#

var list = new int[] { 1, 2, 3, 4, 8, 6, 7, 5 }.ToList();
for (int i = 0; i < list.Count; i++)
{
    if (list[i] % 2 == 0)
        list.RemoveAt(i--); // <-- see what I did here!
}

foreach (var item in list)
{
    Console.WriteLine(item);
}