Question

I am trying to pull out data from an XML document that seems to use relative references like this:

<action>
  <topic reference="../../action[110]/topic"/>
  <context reference="../../../../../../../../../../../../../contexts/items/context[2]"/>
</action>

Two questions:

1. Is this normal or common?
2. Is there a way to handle this with linq to XML / XDocument or would I need to manually traverse the document tree?

---

Edit:

To clarify, the references are to other nodes within the same XML document. The context node above references a list of contexts, and says to get the one at index 2.

The topic node worries me more because it’s referencing a certain other action’s topic, which could in turn reference a list of topics. If that wasn’t happening I would have just loaded the lists of contexts and topics in a cache and looked them up that way.

Answer 1

I ended up manually traversing the tree. But with extension methods it’s all nice and out of the way. In case it might help anyone in the future, this is what I threw together for my use-case:

public static XElement GetRelativeNode(this XAttribute attribute)
    {
        return attribute.Parent.GetRelativeNode(attribute.Value);
    }

    public static string GetRelativeNode(this XElement node, string pathReference)
    {
        if (!pathReference.Contains("..")) return node; // Not relative reference

        var parts = pathReference.Split(new string[] { "/"}, StringSplitOptions.RemoveEmptyEntries);
        XElement current = node;
        foreach (var part in parts)
        {
            if (string.IsNullOrEmpty(part)) continue;
            if (part == "..")
            {
                current = current.Parent;
            } 
            else
            {
                if (part.Contains("["))
                {
                    var opening = part.IndexOf("[");
                    var targetNodeName = part.Substring(0, opening);
                    var ending = part.IndexOf("]");
                    var nodeIndex = int.Parse(part.Substring(opening + 1, ending - opening - 1));

                    current = current.Descendants(targetNodeName).Skip(nodeIndex-1).First();
                } 
                else
                {
                    current = current.Element(part);    
                }

            }
        }

        return current;
    }

And then you’d use it like this (item is an XElement):

item.Element("topic").Attribute("reference").GetRelativeNode().Value