How could I find the string position (index) from an XPath statement?

Question

This question is close, but it's looking for the ordinal position. I'm looking for the actual index position in a given source string.

Better Explanation:

I have the following string

"<a>
    <b>zyx</b>
    <b>wvu</b>
    <b>tsr</b>
    <b>qpo</b>
</a>"

I'm loading that string into a .NET XmlDocument object. Carriage Returns and Line Fees may be a factor here.

Dim xmlSearchText As New XmlDocument()
xmlSearchText.LoadXml(SearchTextBox.Text)

Dim selectedNode As XmlNode = xmlSearchText.SelectSingleNode(txtSearch.Text)

The following XPath Statement could be used to find the 3rd node:

a/b[.='tsr']

However, I need it to return a string index of 23 rather than the ordinal position of 3.

Possible? Not Possible?

Answer 1

Does this give you what you want?

selectedNodenode = xmlSearchText.SelectSingleNode("a/b[.='tsr']");
selectedNode.ParentNode.OuterXml.IndexOf(selectedNode.OuterXml)

Won't give you the index from the root, but it'll give you the index from the parent node.

Answer 2

Using XPathDocument instead of XmlDocument will let you access the IXmlLineInfo interface with line number and column position.

XPathDocument document = new XPathDocument("file.xml");
XPathNavigator navigator = document.CreateNavigator();
XPathNavigator node = navigator.Select("a/b[.='tsr']");
IXmlLineInfo info = ((IXmlLineInfo)node);
Console.WriteLine("Found at ({0},{1})",info.LineNumber,info.LinePosition);

If you really need the character index from the string, you can deduce it by counting newlines int the string and adding the column.