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How to: Find Elements with a Specific Attribute (XPath-LINQ to XML)

Sometimes you want to find all elements that have a specific attribute. You are not concerned about the contents of the attribute. Instead, you want to select based on the existence of the attribute.

The XPath expression is:

./*[@Select]

The following code selects just the elements that have the Select attribute.

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);

This example produces the following output:

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