How to differentiate between two exactly same elements at different parent hierarchy in xml using XDocument

Question

I have an xml like the following:

<return>
  <exams>
    <remove>
    </remove>
    <add>
        <exam errorCode="0" examRef="1" />
    </add>
    <add>
        <exam errorCode="0" examRef="1" />
        <exam errorCode="0" examRef="1" />
    </add>
  </exams>
</return>

and I am building a utility that can differentiate between each node by its extracting its ancestor hierarchy. eg:

return[0].exams[0].add[0].exam[0] //This indicates the first exam node in the first add element.
return[0].exams[0].add[1].exam[0] //This indicates the first exam node in the second add element.
return[0].exams[0].add[1].exam[1] //This indicates the second exam node in the second add element.

and so on. The code that I have so far is:

    private string GetAncestorNodeAsString(XElement el)
    {
        string ancestorData = string.Empty;

        el.Ancestors().Reverse().ToList().ForEach(anc =>
        {
            if (ancestorData == string.Empty)
            {
                ancestorData = String.Format("{0}[0]", anc.Name.ToString());
            }
            else
            {
                ancestorData = String.Format("{0}.{1}[0]", ancestorData, anc.Name.ToString());
            }
        });

        if (ancestorData == string.Empty)
        {
            ancestorData = el.Name.ToString();
        }
        else
        {
            ancestorData = String.Format("{0}.{1}[0]", ancestorData, el.Name.ToString());
        }
        return ancestorData;
    }

This code returns something like:

return[0].exams[0].add[0].exam[0] //zeros here are hardcoded in the code and I need some mechanism to get the position of each of the element in the xml.

I can build up position of elements like:

            var elements = el.Elements().Select((e, index) => new
            {
                node = e,
                position = index
            });

but this will only give me position of only immediate child elements within an element. I need to identify all ancestors and its position in the xml.

Can anyone help please?

Answer 1

Here is method which will return index of element:

private int GetElementIndex(XElement e)
{
    return e.NodesBeforeSelf().OfType<XElement>().Count(x => x.Name == e.Name);
}

And your modified code. Keep in mind - I use AncestorsAndSelf to use single loop. Also I avoided creating list of elements. And used StringBuilder to aggregate result and avoid creation of strings.

private static string GetAncestorNodeAsString(XElement e)
{
    return e.AncestorsAndSelf().Reverse()
            .Aggregate(
               new StringBuilder(),
               (sb, a) => sb.AppendFormat("{0}{1}[{2}]", 
                          sb.Length == 0 ? "" : ".", a.Name, GetElementIndex(a)),
               sb => sb.ToString());
}

Answer 2

Use a recursive method:

private static string GetAncestorNodeAsString(XElement el)
{
    if (el.Parent == null)
        return String.Format("{0}[0]", el.Name.LocalName);
    else
        return String.Format("{0}.{1}[{2}]", 
            GetAncestorNodeAsString(el.Parent), 
            el.Name.LocalName, 
            el.ElementsBeforeSelf().Count(e => e.Name == el.Name));
}