How to find preceding siblings (LINQ to XML)
This article shows how to use XPathSelectElements along the preceding-sibling axis to find sibling elements that precede a given element, and how to use XNode.ElementsBeforeSelf to find the same elements.
Example: Use two methods to find sibling elements that precede an element
The following example finds the FullAddress
element in XML document Sample XML file: Customers and orders, and retrieves the preceding sibling elements in two different ways. It then compares the results and finds them identical.
Note
Both methods provide results that are in document order.
The XPath expression used is preceding-sibling::*
.
XElement co = XElement.Load("CustomersOrders.xml");
XElement add = co.Element("Customers").Element("Customer").Element("FullAddress");
// LINQ to XML query
IEnumerable<XElement> list1 = add.ElementsBeforeSelf();
// XPath expression
IEnumerable<XElement> list2 = add.XPathSelectElements("preceding-sibling::*");
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 list2)
Console.WriteLine(el);
Dim co As XElement = XElement.Load("CustomersOrders.xml")
Dim add As XElement = co.<Customers>.<Customer>. _
<FullAddress>.FirstOrDefault
' LINQ to XML query
Dim list1 As IEnumerable(Of XElement) = add.ElementsBeforeSelf()
' XPath expression
Dim list2 As IEnumerable(Of XElement) = add.XPathSelectElements("preceding-sibling::*")
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 list2
Console.WriteLine(el)
Next
This example produces the following output:
Results are identical
<CompanyName>Great Lakes Food Market</CompanyName>
<ContactName>Howard Snyder</ContactName>
<ContactTitle>Marketing Manager</ContactTitle>
<Phone>(503) 555-7555</Phone>
See also
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