Extensions.Ancestors<T> Method (IEnumerable<T>)

 

Returns a collection of elements that contains the ancestors of every node in the source collection.

Namespace:   System.Xml.Linq
Assembly:  System.Xml.Linq (in System.Xml.Linq.dll)

public static IEnumerable<XElement> Ancestors<T>(
	this IEnumerable<T> source
)
where T : XNode

Parameters

source
Type: System.Collections.Generic.IEnumerable<T>

An IEnumerable<T> of XNode that contains the source collection.

Return Value

Type: System.Collections.Generic.IEnumerable<XElement>

An IEnumerable<T> of XElement that contains the ancestors of every node in the source collection.

Type Parameters

T

The type of the objects in source, constrained to XNode.

If multiple nodes in the source collection have the same ancestor, the ancestor will be included multiple times in the result collection. To avoid this, use the Distinct method.

This method uses deferred execution.

The following example retrieves a collection of the great grandchildren elements. It then uses this axis method to retrieve all ancestors of all elements in the collection.


                XElement xmlTree = new XElement("Root",
    new XElement("Child1",
        new XElement("GrandChild1",
            new XElement("GreatGrandChild1", "content")
        )
    ),
    new XElement("Child2",
        new XElement("GrandChild2",
            new XElement("GreatGrandChild2", "content")
        )
    )
);
IEnumerable<XElement> greatGrandChildren =
    from el in xmlTree.Descendants()
    where el.Name.LocalName.StartsWith("Great")
    select el;

Console.WriteLine("Great Grand Children Elements");
Console.WriteLine("----");
foreach (XElement de in greatGrandChildren)
    Console.WriteLine(de.Name);

IEnumerable<XElement> allAncestors =
    from el in greatGrandChildren.Ancestors().Distinct()
    select el;

Console.WriteLine("");
Console.WriteLine("Ancestors");
Console.WriteLine("----");
foreach (XElement de in allAncestors)
    Console.WriteLine(de.Name);

This example produces the following output:

Great Grand Children Elements
----
GreatGrandChild1
GreatGrandChild2

Ancestors
----
GrandChild1
Child1
Root
GrandChild2
Child2

The following is the same example, but in this case the XML is in a namespace. For more information, see Working with XML Namespaces.


                XNamespace aw = "http://www.adventure-works.com";
XElement xmlTree = new XElement(aw + "Root",
    new XElement(aw + "Child1",
        new XElement(aw + "GrandChild1",
            new XElement(aw + "GreatGrandChild1", "content")
        )
    ),
    new XElement(aw + "Child2",
        new XElement(aw + "GrandChild2",
            new XElement(aw + "GreatGrandChild2", "content")
        )
    )
);
IEnumerable<XElement> greatGrandChildren =
    from el in xmlTree.Descendants()
    where el.Name.LocalName.StartsWith("Great")
    select el;

Console.WriteLine("Great Grand Children Elements");
Console.WriteLine("----");
foreach (XElement de in greatGrandChildren)
    Console.WriteLine(de.Name);

IEnumerable<XElement> allAncestors =
    from el in greatGrandChildren.Ancestors().Distinct()
    select el;

Console.WriteLine("");
Console.WriteLine("Ancestors");
Console.WriteLine("----");
foreach (XElement de in allAncestors)
    Console.WriteLine(de.Name);

This example produces the following output:

Great Grand Children Elements
----
{http://www.adventure-works.com}GreatGrandChild1
{http://www.adventure-works.com}GreatGrandChild2

Ancestors
----
{http://www.adventure-works.com}GrandChild1
{http://www.adventure-works.com}Child1
{http://www.adventure-works.com}Root
{http://www.adventure-works.com}GrandChild2
{http://www.adventure-works.com}Child2

Universal Windows Platform
Available since 8
.NET Framework
Available since 3.5
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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