How to: Find a Union of Two Location Paths (XPath-LINQ to XML)

XPath allows you to find the union of the results of two XPath location paths.

The XPath expression is:

//Category|//Price

You can achieve the same results by using the Concat standard query operator.

Example

This example finds all of the Category elements and all of the Price elements, and concatenates them into a single collection. Note that the LINQ to XML query calls InDocumentOrder to order the results. The results of the XPath expression evaluation are also in document order.

This example uses the following XML document: Sample XML File: Numerical Data (LINQ to XML).

XDocument data = XDocument.Load("Data.xml");

// LINQ to XML query
IEnumerable<XElement> list1 =
    data
    .Descendants("Category")
    .Concat(
        data
        .Descendants("Price")
    )
    .InDocumentOrder();

// XPath expression
IEnumerable<XElement> list2 = data.XPathSelectElements("//Category|//Price");

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 data As XDocument = XDocument.Load("Data.xml")

' LINQ to XML query
Dim list1 As IEnumerable(Of XElement) = _
    data...<Category>.Concat(data...<Price>).InDocumentOrder()

' XPath expression
Dim list2 As IEnumerable(Of XElement) = _
    data.XPathSelectElements("//Category|//Price")

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
<Category>A</Category>
<Price>24.50</Price>
<Category>B</Category>
<Price>89.99</Price>
<Category>A</Category>
<Price>4.95</Price>
<Category>A</Category>
<Price>66.00</Price>
<Category>B</Category>
<Price>.99</Price>
<Category>A</Category>
<Price>29.00</Price>
<Category>B</Category>
<Price>6.99</Price>

See Also

Concepts

LINQ to XML for XPath Users

Build Date:

2012-08-02