Powershell select XML nodes where attribute contained in array

Question

Say I have structures like:

[xml]$i = "
<root>
    <item>
        <id>1</id>
        <data>Content_Of_1</data>
    </item>
    <item>
        <id>2</id>
        <data>Content_Of_2</data>
<item>
    <id>5</id>
    <data>Content_Of_5</data>
</item>
    </item>
</root>
"

$foo = @(1,2,3)

And I want to select $i.root.item.data where $i.root.item.id is in $foo.

To select the nodes matching IDs in the array I can do:

($i.root.item | ? {$foo -contains $_.id})

But for some reason if I try to get at $_.data, I get nothing:

($i.root.item | ? {$foo -contains $_.id}).data

Why?

Original phrasing invited alternative xpath solutions. I have since got close w/o xpath, but xpath solutions stil welcome. — Yevgeniy
– Yevgeniy, Commented Oct 24, 2012 at 16:29
First of all replace you item tag by "items", as far as I remember it exists a problem linked with the fact that "item" is already used as an object property. — JPBlanc
– JPBlanc, Commented Oct 24, 2012 at 16:36

dugas · Accepted Answer · 2012-10-24 16:45:00Z

1

But for some reason if I try to get at $_.data, I get nothing:

($i.root.item | ? {$foo -contains $_.id}).data

The reason you get nothing is you are trying to access a property (data) on the whole collection where it does not exist. You need to do the following:

$i.root.item | ? {$foo -contains $_.id} | ForEach-Object { $_.data }

Which accesses the data property on each object. You could also select the values in the data property for each object:

$i.root.item | ? {$foo -contains $_.id} | Select-Object data

Which would produce an array of PSCustomObjects where each object would contain a single property named data (as opposed to a string array as the ForEach-Object example would).

Note that in Powershell 3.0, with the new property enumeration feature, your original syntax would produce the desired result as the enumeration would automatically be done.

edited Oct 24, 2012 at 16:45

answered Oct 24, 2012 at 16:37

dugas

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2 Comments

Yevgeniy Over a year ago

Thanks! Is there any way to do this without a foreach loop?

dugas Over a year ago

@Yevgeniy - updated answer with option of using Select-Object.

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