Using XPath to add elements to mutiple elements doesn't work as intended

Question

My logic goes as follows: I want to find the first element that misses a given attribute, add the attribute and then find the next element which misses the element, add it and so fourth.

I find the first element missing the amount attribute in the following way:

    private XmlNode GetFirstElementWithoutAmount()
            {
                string productXPathQuery = "//XML/Products";
                XmlNodeList productList = ParentXmlDocument.SelectNodes(productXPathQuery);
                foreach (XmlNode element in productList)
                {
                    string passengerXPathQuery = "//XML/Products[ID=" + element.FirstChild.InnerText + "]/Amount";
                    var amount = element.SelectSingleNode(passengerXPathQuery);
                    if (amount == null)
                    {
                        return element;
                    }
                }

                return null;
     }

When I've found the first element missing the attribute, the amount is added in the following way:

private XmlNode GetOrCreateChildXMLNode(string NewNodeName, XmlNode ParentXMLNode)
        {

            if (ParentXMLNode == null)
            {
                return null;
            }

            XmlNode NewXMLNode = ParentXMLNode.SelectSingleNode("//" + NewNodeName);
            if (NewXMLNode == null)
            {
                NewXMLNode = ParentXmlDocument.CreateNode(XmlNodeType.Element, NewNodeName, string.Empty);
                ParentXMLNode.AppendChild(NewXMLNode);
            }

            return NewXMLNode;
        }

The problems is, that it only adds to the first element, and then the first function always returns the second element, even though there's more elements to come? Any ideas why this is?

https://stackoverflow.com/questions/10053928/do-double-slash-in-xpath-predicate-work-the-same-as-in-the-path-itself is more or less canonical answer to "why when I search from the root (using `//`) it always finds the same node"... — Alexei Levenkov, Dec 06 '19 at 01:25

Ed Bangga · Accepted Answer · 2019-12-06T00:53:40.513

0

You are already inside //XML/Products during your foreach loop. Point directly to subnode.

string passengerXPathQuery = "./Amount";

edited Dec 06 '19 at 00:53

answered Dec 06 '19 at 00:26

Ed Bangga

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What about the ID then? – Recusiwe Dec 06 '19 at 00:37
You don't need the ID, because you are already selecting everything in /products. – Ed Bangga Dec 06 '19 at 00:39
It iterates the element all good, but only appends to the first. It looks like it thinks it's already added when processing the following. – Recusiwe Dec 06 '19 at 00:42
will you able to share your sample xml? – Ed Bangga Dec 06 '19 at 00:45
It seems like amount doesn't get reset. So it only return the element processing the first node. – Recusiwe Dec 06 '19 at 00:48
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/203711/discussion-between-recusiwe-and-). – Recusiwe Dec 06 '19 at 00:56

Using XPath to add elements to mutiple elements doesn't work as intended

1 Answers1