How can I remove duplicate, invalid, child nodes from an XML document using Linq to XML?

Question

I'm creating XML from JSON retrieved from an HttpWebRequest call, using JsonConvert. The JSON I'm getting back sometimes has duplicate nodes, creating duplicate nodes in the XML after conversion, which I then have to remove.

The processing of the JSON to XML conversion is being done in a generic service call wrapper that has no knowledge of the underlying data structure and so can't do any XPath queries based on a named node. The duplicates could be at any level within the XML.

I've got to the stage where I have a list of the names of duplicate nodes at each level but am not sure of the Linq query to use this to remove all but the first node with that name.

My code:

protected virtual void RemoveDuplicateChildren(XmlNode node)
{
    if (node.NodeType != XmlNodeType.Element || !node.HasChildNodes)
    {
        return;
    }

    var xNode = XElement.Load(node.CreateNavigator().ReadSubtree());
    var duplicateNames = new List<string>();

    foreach (XmlNode child in node.ChildNodes)
    {
        var isBottom = this.IsBottomElement(child); // Has no XmlNodeType.Element type children

        if (!isBottom)
        {
            this.RemoveDuplicateChildren(child);
        }
        else
        {
            var count = xNode.Elements(child.Name).Count();

            if (count > 1 && !duplicateNames.Contains(child.Name))
            {
                duplicateNames.Add(child.Name);
            }
        }
    }

    if (duplicateNames.Count > 0)
    {
        foreach (var duplicate in duplicateNames)
        {
            xNode.Elements(duplicate).SelectMany(d => d.Skip(1)).Remove();

        }
    }
}

The final line of code obviously isn't correct but I can't find an example of how to rework it to retrieve and then remove all but the first matching element.

UPDATE: I have found two ways of doing this now, one using the XElement and one the XmlNode, but neither actually removes the nodes.

Method 1:-

foreach (var duplicate in duplicateNames)
{
    xNode.Elements(duplicate).Skip(1).Remove();
}

Method 2:-

foreach (var duplicate in duplicateNames)
{
    var nodeList =  node.SelectNodes(duplicate);

    if (nodeList.Count > 1)
    {
        for (int i=1; i<nodeList.Count; i++)
        {
            node.RemoveChild(nodeList[i]);
         }
     }
}

What am I missing?

Answer 1

If you don't want any duplicate names: (assuming no namespaces)

XElement root = XElement.Load(file); // .Parse(string)
List<string> names = root.Descendants().Distinct(x => x.Name.LocalName).ToList();
names.ForEach(name => root.Descendants(name).Skip(1).Remove());
root.Save(file); // or root.ToString()