The Moth

Recently I was playing with some LINQ to XML for a demo I was preparing and was having trouble retrieving the expected values from what was a very straightforward query.

Have a look at the XML file that looks like this (the results of programmatically calling this Amazon service).

Each Item element represents a book and I wanted to retrieve the Title. How would you form that query with LINQ to XML?

I went for the obvious:

  var res =
    from ia in XElement.Parse(e.Result).DescendantsAndSelf("ItemAttributes")
    select ia.Element("Title").Value;

When that did not produce the expected results I scratched my "tired" head at the time and pinged MikeT who came up with the correct way of doing this (you still have time to work it out on your own).

The clue (and at the same time further "excuse") is that all my previous experiments with LINQ to XML involved using my own demo XML files that never had namespaces inside so I forgot all about them (haven't paid the tax in a while). I find quite ugly what you have to do to incorporate namespaces in a LINQ to XML query, but there seems to be no nicer alternative to the following (thanks Mike):

void SomeMethod()
{
  var res =
    from ia in XElement.Parse(e.Result).DescendantsAndSelf(n("ItemAttributes"))
    select ia.Element(n("Title")).Value;

  // TODO use res
}

static XName n(string name)
{
  return XNamespace.Get("http://webservices.amazon.com/AWSECommerceService/2005-10-05") + name;
}

I still didn't like this solution for the simple demo I wanted to use it for. So, I recalled VB's superior support for XML and I converted the project to VB and used the following instead which needs no extra method and is all round more elegant:

  Dim res = _
    From ia In XElement.Parse(e.Result)...<n:ItemAttributes> _
    Select ia...<n:Title>.Value()

...and if you are wondering where the n comes from, that is at the top of the VB file:

Imports <xmlns:n="http://webservices.amazon.com/AWSECommerceService/2005-10-05">

...another aspect of VB's beauty and another thing I had the opportunity to mention in my demo ;-)