How can I extract specific tags using LINQ to XML in F#?

Question

I have an XML file, which I open in F# like this:

let Bookmarks(xmlFile:string) = 
    let xml = XDocument.Load(xmlFile)

Once I have the XDocument I need to navigate it using LINQ to XML and extract all specific tags. Part of my solution is:

let xname (tag:string) = XName.Get(tag)
let tagUrl (tag:XElement) = let attribute = tag.Attribute(xname "href")
                            attribute.Value
let Bookmarks(xmlFile:string) = 
    let xml = XDocument.Load(xmlFile)
    xml.Elements <| xname "A" |> Seq.map(tagUrl)

How can I extract the specific tags from the XML file?

Answer 1

#light
open System
open System.Xml.Linq

let xname s = XName.Get(s)
let bookmarks (xmlFile : string) = 
    let xd = XDocument.Load xmlFile
    xd.Descendants <| xname "bookmark"

This will find all the descendant elements of "bookmark". If you only want direct descendants, use the Elements method (xd.Root.Elements <| xname "whatever").

Answer 2

Caveat: I've never done linq-to-xml before, but looking through other posts on the topic, this snippet has some F# code that compiles and does something, and thus it may help you get started:

open System.IO
open System.Xml
open System.Xml.Linq 

let xmlStr = @"<?xml version='1.0' encoding='UTF-8'?>
<doc>
    <blah>Blah</blah>
    <a href='urn:foo' />
    <yadda>
        <blah>Blah</blah>
        <a href='urn:bar' />
    </yadda>
</doc>"

let xns = XNamespace.op_Implicit ""
let a = xns + "a"
let reader = new StringReader(xmlStr)
let xdoc = XDocument.Load(reader)
let aElements = [for x in xdoc.Root.Elements() do
                 if x.Name = a then
                     yield x]
let href = xns + "href"
aElements |> List.iter (fun e -> printfn "%A" (e.Attribute(href)))