Question

<root>
  <data name="ID1"></data>
  <data name="ID2"></data>
</root>

XDocument xmlDoc = XDocument.Load(xmlFile);

bool exists = (from elem in xmlDoc.Descendants("root")
               where elem.Element("data").Attribute("name").Value == "ID1"
               select elem).Any();

It doesn’t see that ID1 already exists. What am I doing wrong?

Answer 1

Based on what you’ve shown, first I have to point out that the XML snippet is not valid XML. The data nodes are not closed.

Assuming this is a valid XML document, it would ultimately depend on what the type is for your variable XMLDoc.

If it was an XDocument, then that code snippet should work and the value of exists would be true. The document contains a descendant called root and it could go about its business.

If it was an XElement on the other hand, then that code snippet should fail and the value of exists would be false. The XMLDoc variable would be referring to the root element already and there clearly isn’t any descendants called root.

You should rewrite your query however, maybe something more like this:

// please follow .NET naming conventions and use lowercase for local variables
XDocument xmlDoc = XDocument.Load(xmlFile);

// iterate over the `data` elements, not the `root` elements
bool exists = (from data in xmlDoc.Element("root").Elements("data")
               where (string)data.Attribute("name") == "ID1"
               select data).Any();
// using the cast is a personal style choice
// using `XAttribute.Value` is fine too in this case