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How to find an attribute of the parent (LINQ to XML)

This article shows how to use XPathEvaluate to find an attribute of a parent element, and how to use LINQ to XML query to do the same thing.

Example: Find the Author element, and then find the id attribute of its parent

This example first finds an Author element in XML document Sample XML file: Books, and then finds the id attribute of its parent element.

The XPath expression is ../@id.

XDocument books = XDocument.Load("Books.xml");

XElement author =
    books
    .Root
    .Element("Book")
    .Element("Author");

// LINQ to XML query
XAttribute att1 =
    author
    .Parent
    .Attribute("id");

// XPath expression
XAttribute att2 = ((IEnumerable)author.XPathEvaluate("../@id")).Cast<XAttribute>().First();

if (att1 == att2)
    Console.WriteLine("Results are identical");
else
    Console.WriteLine("Results differ");
Console.WriteLine(att1);

Dim books As XDocument = XDocument.Load("Books.xml")
Dim author As XElement = books.Root.<Book>.<Author>.FirstOrDefault()

' LINQ to XML query
Dim att1 As XAttribute = author.Parent.Attribute("id")

' XPath expression
Dim att2 As XAttribute = DirectCast(author.XPathEvaluate("../@id"),  _
    IEnumerable).Cast(Of XAttribute)().First()

If att1 Is att2 Then
    Console.WriteLine("Results are identical")
Else
    Console.WriteLine("Results differ")
End If
Console.WriteLine(att1)

This example produces the following output:

Results are identical
id="bk101"

See also