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How to find elements with a specific attribute (LINQ to XML)

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This article shows how to use XPathEvaluate to find all elements that have a specific attribute (regardless of value), and how to use LINQ to XML query to do the same thing.

Example: Find all elements that have the Select attribute

The following example creates an XML tree and then finds the elements that have the Select attribute.

The XPath expression is ./*[@Select].

XElement doc = XElement.Parse(
@"<Root>
    <Child1>1</Child1>
    <Child2 Select='true'>2</Child2>
    <Child3>3</Child3>
    <Child4 Select='true'>4</Child4>
    <Child5>5</Child5>
</Root>");

// LINQ to XML query
IEnumerable<XElement> list1 =
    from el in doc.Elements()
    where el.Attribute("Select") != null
    select el;

// XPath expression
IEnumerable<XElement> list2 =
    ((IEnumerable)doc.XPathEvaluate("./*[@Select]")).Cast<XElement>();

if (list1.Count() == list2.Count() &&
        list1.Intersect(list2).Count() == list1.Count())
    Console.WriteLine("Results are identical");
else
    Console.WriteLine("Results differ");
foreach (XElement el in list1)
    Console.WriteLine(el);

Dim doc As XElement = _
    <Root>
        <Child1>1</Child1>
        <Child2 Select='true'>2</Child2>
        <Child3>3</Child3>
        <Child4 Select='true'>4</Child4>
        <Child5>5</Child5>
    </Root>

' LINQ to XML query
Dim list1 As IEnumerable(Of XElement) = _
    From el In doc.Elements() _
    Where el.@Select <> Nothing _
    Select el

' XPath expression
Dim list2 As IEnumerable(Of XElement) = DirectCast(doc.XPathEvaluate _
    ("./*[@Select]"), IEnumerable).Cast(Of XElement)()

If list1.Count() = list2.Count() And _
    list1.Intersect(list2).Count() = list1.Count() Then
    Console.WriteLine("Results are identical")
Else
    Console.WriteLine("Results differ")
End If

For Each el As XElement In list1
    Console.WriteLine(el)
Next

This example produces the following output:

Results are identical
<Child2 Select="true">2</Child2>
<Child4 Select="true">4</Child4>

See also