为什么此代码无法在xml元素中找到任何重复项?

这是输入的xml:

<?xml version="1.0"?>
<StateSeparationRequestCollection xsi:schemaLocation="https://uidataexchange.org/schemas SeparationRequest.xsd" xmlns="https://uidataexchange.org/schemas" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <StateSeparationRequest>
    <StateRequestRecordGUID>30000000000000000000000000004000</StateRequestRecordGUID>
        <SSN>999999999</SSN>
    </StateSeparationRequest>
    <StateSeparationRequest>
    <StateRequestRecordGUID>30000000000000000000000000004000</StateRequestRecordGUID>
        <SSN>999999999</SSN>
    </StateSeparationRequest>
</StateSeparationRequestCollection>

我试图在StateRequestRecordGUID上找到重复的元素值，如果找到重复的，请将其从文档中删除.

I am trying to find duplicate element Values at StateRequestRecordGUID, and if duplicates are found, remove them from the document.

这是我的代码:

XDocument doc = XDocument.Load(xmlreader);
XNamespace ns = "https://uidataexchange.org/schemas";

var duplicates = (from req in doc.Descendants(ns + "StateSeparationRequest")
                  group req by req.Descendants(ns + "StateRequestRecordGUID").First().Value
                  into g
                  where g.Count() > 1
                  select g.Skip(1)).SelectMany(elements => elements);
foreach (var duplicate in duplicates)
{
    duplicate.Remove();
}

var node = doc.Descendants(ns + "EmployerTPASeparationRequest");
var node2 = node.ElementAt(i);
string _StateRequestRecordGUID = "";

foreach (var element in node2.Elements())
{ ...

这应该是输出:

<?xml version="1.0"?>
<StateSeparationRequestCollection xsi:schemaLocation="https://uidataexchange.org/schemas SeparationRequest.xsd" xmlns="https://uidataexchange.org/schemas" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <StateSeparationRequest>
    <StateRequestRecordGUID>30000000000000000000000000004000</StateRequestRecordGUID>
        <SSN>999999999</SSN>
    </StateSeparationRequest>
</StateSeparationRequestCollection>