XElement and XName crashes when xml has namespace to root node

Question

Hi i was fiddeling around with xml files and i notised something i have a bit problem of solving.

I have a Xml that starts with a root node and then has another child node that can change name for example:

<root>
  <Child1>
</root>

So given that "Child1" can be changed to "Child2" or "Child3" i made this linq be able to extract the name from whatever comes my way.

first:

XElement root = XElement.Parse(xml);

var childType = root.Descendants().First(x => x.Name == "Child1" || x.Name == "Child2"|| x.Name == "Child3").Name;

So when i have my xml without a namespace, as shown above, it workes fine, i manage to extract the name from the node tag.

But when i have a namespace into the root tag it throws an error:

<root xmlns="namespace">
  <Child1>
</root>

That xml going through the same linq, throws:

Sequence contains no matching element

Answer 1

Your root element has a namespace defined ( xmlns="namespace" ) thus all child elements are associated with the same namespace. Ie Child1 element will be in the same namespace, and its name will contain both namespace prefix and local name ( "Child1" ). So you can either specify full name when searching for Child1 element:

var ns = root.GetDefaultNamespace();
var childType = root.Descendants()
   .First(x => x.Name == ns +"Child1" || x.Name == ns + "Child2"|| x.Name == ns + "Child3")
   .Name;

Or you can look for x.Name.LocalName (but I don't recommned this approach, though it's unlikely you will have Child1 elements from another namespace).

Note: your Child element does not have closing tag (probably it's a misprint)

Further reading: Xml Namespaces