How to: Find Preceding Siblings (XPath-LINQ to XML)
This topic compares the XPath preceding-sibling axis to the LINQ to XML child XNode.ElementsBeforeSelf axis.
The XPath expression is:
preceding-sibling::*
Note that the results of both XPathSelectElements and XNode.ElementsBeforeSelf are in document order.
Example
The following example finds the FullAddress element, and then retrieves the previous elements using the preceding-sibling axis.
This example uses the following XML document: Sample XML File: Customers and Orders (LINQ to XML).
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>