Powershell : multiple Select-Object statements returning 1st occurrence results only

Question

I am running PowerShell version 4.0 on Windows 8.1

I have an xml document (from a nifi flow) called flow1.xml as follows:

<flowController encoding-version="1.3">
  <rootGroup>
    <id>123</id>
    <name>BigTime</name>
    <position x="0.0" y= "0.0"/>
    <processGroup>
      <id>456</id>
      <name>SmallTime</name>
      <position x="1000.0" y="2000.0"/>
      <processGroup>
        <id>789</id>
        <name>TinyTime</name>
        <position x="3000.0" y="4000.0"/>
      </processGroup>
    <processGroup/>
  </rootGroup>
</flowController>

I have a powerShell script test.ps1 as follows :

$filePath='flow1.xml'
$xmlDocument = New-Object -TypeName XML
$xmlDocument.Load($filePath)

$xmlDocument.flowController.rootGroup.processGroup |
Where-Object { $_.name -eq 'SmallTime'} |
Select-Object -Property {$_.id}

$xmlDocument.flowController.rootGroup.processGroup.processGroup |
Where-Object { $_.name -eq 'TinyTime'} |
Select-Object -Property {$_.id}

I run from PowerShell within a Windows Cmd box; ie PS C\Temp>test.ps When I run this I get output as expected:

Output:
$_.id
-----
456
789

When I change the 2nd Select_Object thus :

$xmlDocument.flowController.rootGroup.processGroup.processGroup |
Where-Object { $_.name -eq 'TinyTime'} |
Select-Object -Property {$_.name}

I get

Output:
$_.id
-----
456

I get only the $_id from the 1st clause, but not the $_name from the 2nd clause. The general case is - if both Select-Object statements select the same parameter then both are executed correctly. For instance if both Select-Object statements were Select-Object -Property {$_.name} I get the output :

Output:
$_.name
-----
SmallTime
TinyTime

If the Select-Object statements are different it seems to only execute the first one. I tried reading in the xmlDocument again before the 2nd Select-Object :

$filePath='flow1.xml'
$xmlDocument = New-Object -TypeName XML
$xmlDocument.Load($filePath)

$xmlDocument.flowController.rootGroup.processGroup |
Where-Object { $_.name -eq 'SmallTime'} |
Select-Object -Property {$_.id}

$xmlDocument = New-Object -TypeName XML
$xmlDocument.Load($filePath)
$xmlDocument.flowController.rootGroup.processGroup.processGroup |
Where-Object { $_.name -eq 'TinyTime'} |
Select-Object -Property {$_.id}

but the same thing happens. I only get the result of the 1st Select-Object statement.

Does anyone know why this is happening?

Answer 1

Just adding this note for closure.

Don't know what was going wrong with the piping. Colleagues have had similar problems. So I changed tack.

I drilled down into $xmlDocument by setting a new variable: $group = $xmlDocument.flowController.rootGroup.processGroup

and replaced the code with appropriate

foreach ($property in $group.property...){
   if ($property.name -eq 'oldValue'){
     parameter.value = 'newValue'
   }
}

This works, and can be further elaborated/complicated with more complex searches.