Extensions.Ancestors(Of T) Method (IEnumerable(Of T))

.NET Framework (current version)

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)

Syntax

<ExtensionAttribute>
Public Shared Function Ancestors(Of T As XNode) (
	source As IEnumerable(Of T)
) As IEnumerable(Of XElement)

Parameters

source: Type: System.Collections.Generic.IEnumerable(Of T)
An IEnumerable(Of T) of XNode that contains the source collection.

Return Value

Type: System.Collections.Generic.IEnumerable(Of XElement)

An IEnumerable(Of 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.

Remarks

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.

Examples

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.


                Dim xmlTree As XElement = _
    <Root>
        <Child1>
            <GrandChild1>
                <GreatGrandChild1>content</GreatGrandChild1>
            </GrandChild1>
        </Child1>
        <Child2>
            <GrandChild2>
                <GreatGrandChild2>content</GreatGrandChild2>
            </GrandChild2>
        </Child2>
    </Root>

Dim greatGrandChildren = From el In xmlTree.Descendants _
                         Where el.Name.LocalName.StartsWith("Great") _
                         Select el

Console.WriteLine("Great Grand Children Elements")
Console.WriteLine("----")

For Each de As XElement In greatGrandChildren
    Console.WriteLine(de.Name)
Next

Dim allAncestors = From el In greatGrandChildren.Ancestors.Distinct _
                   Select el

Console.WriteLine("")
Console.WriteLine("Ancestors")
Console.WriteLine("----")

For Each de As XElement In allAncestors
    Console.WriteLine(de.Name)
Next

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.


                Imports <xmlns="http://www.adventure-works.com">

Module Module1
    Sub Main()
        Dim xmlTree As XElement = _
            <Root>
                <Child1>
                    <GrandChild1>
                        <GreatGrandChild1>content</GreatGrandChild1>
                    </GrandChild1>
                </Child1>
                <Child2>
                    <GrandChild2>
                        <GreatGrandChild2>content</GreatGrandChild2>
                    </GrandChild2>
                </Child2>
            </Root>

        Dim greatGrandChildren = From el In xmlTree.Descendants _
                                 Where el.Name.LocalName.StartsWith("Great") _
                                 Select el

        Console.WriteLine("Great Grand Children Elements")
        Console.WriteLine("----")

        For Each de As XElement In greatGrandChildren
            Console.WriteLine(de.Name)
        Next

        Dim allAncestors = From el In greatGrandChildren.Ancestors.Distinct _
                           Select el

        Console.WriteLine("")
        Console.WriteLine("Ancestors")
        Console.WriteLine("----")

        For Each de As XElement In allAncestors
            Console.WriteLine(de.Name)
        Next
    End Sub
End Module