PowerShell - xpath 不区分大小写 XML 属性名称

Question

I have a XML where the attribute names can be combinations of lower-case and upper-case letters. In the below example, 'datasource' attribute can have any number of lowercase and uppercase letters.

I need to fetch those nodes where the 'datasource' is XML. I have searched all over the internet, but could not find any solution for this. Several examples are there for translate(), lower-case() but they don't fit my scenario.

[xml] $GM_ProcessXML =@'
<Process>
    <Parameter Name="Parameter1" Datasource="XML"><![CDATA[Sujeet]]></Parameter>
    <Parameter Name="Parameter2" DataSource="XML"><![CDATA[Padhi]]></Parameter>     
    <Parameter Name="Parameter3" DatASource="XML"><![CDATA[Padhi]]></Parameter>     
    <Parameter Name="Parameter4" datASource="XML"><![CDATA[Padhi]]></Parameter>     
    <Node>
        <Node1 Name="Node1" Datasource="XML"><![CDATA[Sujeet]]></Node1>
        <Node2 Name="Node2" DataSource="XML"><![CDATA[Padhi]]></Node2>      
        <Node3 Name="Node3" DatASource="XML"><![CDATA[Padhi]]></Node3>      
        <Node4 Name="Node4" datASource="XML"><![CDATA[Padhi]]></Node4>    
    </Node>
</Process>
'@

$XPath = "//*[@datasource='XML']"

$Nodes = $GM_ProcessXML.SelectNodes($XPath)

$Nodes

Answer 1

You could also use the case-insensitive dot notation like this:

$Nodes = $GM_ProcessXML.Process.Parameter | Where-Object { $_.DAtaSourcE -eq 'xML' }

This will return an array of System.Xml.XmlElement nodes

Answer 2

Short of modifying the files:

[xml]$GM_ProcessXML = @'
<Process>
    <Parameter Name="Parameter1" Datasource="XML"><![CDATA[Sujeet]]></Parameter>
    <Parameter Name="Parameter2" DataSource="XML"><![CDATA[Padhi]]></Parameter>
    <Parameter Name="Parameter3" DatASource="XML"><![CDATA[Padhi]]></Parameter>
    <Parameter Name="Parameter4" datASource="XML"><![CDATA[Padhi]]></Parameter>
    <Node>
        <Node1 Name="Node1" Datasource="XML"><![CDATA[Sujeet]]></Node1>
        <Node2 Name="Node2" DataSource="XML"><![CDATA[Padhi]]></Node2>
        <Node3 Name="Node3" DatASource="XML"><![CDATA[Padhi]]></Node3>
        <Node4 Name="Node4" datASource="XML"><![CDATA[Padhi]]></Node4>
    </Node>
</Process>
'@ -replace 'datasource','datasource'

$XPath = "//*[@datasource='XML']"

$Nodes = $GM_ProcessXML.SelectNodes($XPath)

$Nodes


Name       datasource #cdata-section
----       ---------- --------------
Parameter1 XML        Sujeet
Parameter2 XML        Padhi
Parameter3 XML        Padhi
Parameter4 XML        Padhi
Node1      XML        Sujeet
Node2      XML        Padhi
Node3      XML        Padhi
Node4      XML        Padhi

Answer 3

• There is no case-insensitive string comparison in XPath 1.0
• XPath 1.0 is all that is available in .NET
• PowerShell is based completely on .NET

So, on the face of it, you are out of luck. But there is a work-around by combining PowerShell code and XPath translate() .

[xml] $GM_ProcessXML =@'
<Process>
    <Parameter Name="Parameter1" Datasource="XML"><![CDATA[Sujeet]]></Parameter>
    <Parameter Name="Parameter2" DataSource="XML"><![CDATA[Padhi]]></Parameter>     
    <Parameter Name="Parameter3" DatASource="XML"><![CDATA[Padhi]]></Parameter>     
    <Parameter Name="Parameter4" datASource="XML"><![CDATA[Padhi]]></Parameter>     
    <Node>
        <Node1 Name="Node1" Datasource="XML"><![CDATA[Sujeet]]></Node1>
        <Node2 Name="Node2" DataSource="XML"><![CDATA[Padhi]]></Node2>      
        <Node3 Name="Node3" DatASource="XML"><![CDATA[Padhi]]></Node3>      
        <Node4 Name="Node4" datASource="XML"><![CDATA[Padhi]]></Node4>    
    </Node>
</Process>
'@

$attributeName = 'DataSource'
$lc = $attributeName.ToLowerInvariant()    # -> 'datasource'
$uc = $attributeName.ToUpperInvariant()    # -> 'DATASOURCE'

$XPath = "//*[@*[translate(name(), '$uc', '$lc') = '$lc'] = 'XML']"
# ->      //*[@*[translate(name(), 'DATASOURCE', 'datasource') = 'datasource'] = 'XML']

$Nodes = $GM_ProcessXML.SelectNodes($XPath)

Of course you can write the translate function by hand, especially in cases where the string to translate is basically hard-coded.

But this approach is generic, so you can also use it to search case-insensitively for any user-provided/dynamic value, eg:

$value = 'sujeet'   # as the user has entered it

$lc = $value.ToLowerInvariant()
$uc = $value.ToUpperInvariant()

$XPath = "//Parameter[translate(., '$uc', '$lc') = '$lc']"
# ->      //Parameter[translate(., 'SUJEET', 'sujeet') = 'sujeet']

This is a lot better than the often-proposed

translate(., 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz')

since that is limited to pre-defined alphabets, and fails for eg accented characters unless you explicitly include them, which quickly becomes unwieldy.