PowerShell advanced function output PipelineVariable doesn't work -

i created advanced function mac address vm running on vmware esxi.

function get-macfromvm {     [cmdletbinding(supportsshouldprocess=$true)]     param(         # name of vm of want obtain mac address.         [parameter(mandatory=$true,                    valuefrompipeline=$true,                    valuefrompipelinebypropertyname=$true)]         [string[]]         $name     )      begin {}     process {         foreach ($item in $name) {             if ($pscmdlet.shouldprocess($item, "getting mac address")) {                 get-vm $item -pipelinevariable vm |                      get-networkadapter |                      select-object @{n="name"; e={$vm.name}},                         @{n="clientid"; e={$_.macaddress -replace ":","-"}}             }         }       }     end {} } 

so far works perfect. can use in of following ways , results back.

it accepts either single or array of string via named parameter or pipeline input.

get-macfromvm -name "playground" get-macfromvm -name "playground", "dc01" "playground", "dc01" | get-macfromvm 

the output [pscustomobject] 2 properties, name , clientid.

now problem starts when want chain result multiple other cmdlets using -pipelinevariable parameter.

normally should able use this:

get-macfromvm -name "playground" -pipelinevariable pv | % {$pv} 

but doesn't show me results back. if substitute $pv $_ show correct result, cannot use automatic variable 2 or 3 cmdlets farther in pipeline chain.

although can solve using -outvariable and/or split multiple lines. want know why doesn't work, want know i'm missing here.

i have no experience -pipelinevariable parameter. so, took opportunity learn -pipelinevariable parameter:

because not have easy access vms either, simulated function follows:

function get-macfromvm {     [cmdletbinding(supportsshouldprocess=$true)]     param(         [parameter(mandatory=$true,                    valuefrompipeline=$true,                    valuefrompipelinebypropertyname=$true)]         [string[]]         $name     )     function macaddress {(1..4 | foreach {'{0:x2}' -f (get-random -min 0 -max 255)}) -join ":"}     function get-vm {[cmdletbinding()] param ($name) [pscustomobject]@{name = $name; macaddress = (macaddress)}}     foreach ($item in $name) {         if ($pscmdlet.shouldprocess($item, "getting mac address")) {             get-vm $item -pipelinevariable vm |             select-object @{n="name"; e={$vm.name}}, @{n="clientid"; e={$_.macaddress -replace ":","-"}}         }     } } 

but not able reproduce issue:

ps c:\> get-macfromvm -name "playground", "dc01" -pipelinevariable pv | % {$pv}  name       clientid ----       -------- playground 3c-23-55-c4 dc01       4f-38-42-a7 

so wonder if simulated function works you.
if yes, maybe can find differences real vm object.

knowing powershell, question whether there nothing outputted or nothing displayed. happens if output single property:

get-macfromvm -name "playground" -pipelinevariable pv | % {$pv.name} 

or:

get-macfromvm -name "playground" -pipelinevariable pv | % {$pv.gettype()} 

does return "you cannot call method on null-valued expression." error?