powershell v7 - Function pipeline issue - powershell

Question

I'm trying to write 2 functions:
the first one (Get-Lab) retrieves a [Lab] object
the second one (remove-Lab) remove a [Lab] object
[Lab] is a class defined in my module.
When a run Get-Lab I correctly retrieve my lab instance with the correct type :
When I run Remove-Lab -Lab (Get-Lab -Name Mylab), the operation is correctly performed:
But when I try to pass the [Lab] object through the pipeline it fails.
The function does not receive the object through the pipeline. However I've set the -Lab Parameter as mandatory with ValueFromPipeline=$true.
Function Remove-Lab{
[CmdletBinding(DefaultParameterSetName='Lab')]
param (
[Parameter(ValueFromPipeline=$true,ParameterSetName='Lab',Position=0,Mandatory=$true)]
[Lab]
$Lab,
# Parameter help description
[Parameter(Position=1,Mandatory=$false)]
[switch]
$Force=$false
)
begin {
Write-host ("`tLabName : {0}" -f $Lab.Name) -ForegroundColor Yellow
if ($null -ne $Lab) {
$LabToRemove = $Lab
}
if (-not [string]::IsNullOrEmpty($LabId)) {
$LabToRemove = Get-Lab -Id $LabId
}
if (-not [string]::IsNullOrEmpty($Name)) {
$LabToRemove = Get-Lab -Name $Name
}
if ($null -eq $LabToRemove) {
throw "There is no Lab with specified characteristics. Please check your input"
}
}
process {
$DoRemoval = $true
if ($Force.IsPresent -eq $false) {
while ($null -eq $UserInput -or $UserInput -notin #('Y','N')) {
$UserInput = Read-HostDefault -Prompt "Are you sure want to remove the selected Lab and all its components ? [Y]es, [N]o" -Default 'N'
if ($UserInput -eq 'N') {
$DoRemoval = $false
}
}
Write-Host ("`tUser Input : {0}" -f $UserInput) -ForegroundColor Green
}
if ($DoRemoval -eq $true) {
Write-Host ("`tAbout to Remove the following Lab : {0}" -f $LabToRemove.Name) -ForegroundColor Green
}
}
end {
}
}
As you can see below when a debug this function, the $Lab Parameter is null.
Do you have any idea about this issue ?

Answer 1

Since the function is testing on $LabId or $Name, these variables need to exist in the function and at the moment they do not.
Try changing the parameters to:
[CmdletBinding(DefaultParameterSetName='LabId')]
param (
[Parameter(ValueFromPipeline=$true, ValueFromPipelineByPropertyName = $true, ParameterSetName='LabId',Position=0,Mandatory=$true)]
[string]$LabId,
[Parameter(ValueFromPipeline=$true, ValueFromPipelineByPropertyName = $true, ParameterSetName='LabName',Position=0,Mandatory=$true)]
[string]$Name,
# Parameter help description
[switch]$Force # no need to set a switch to $false because if you don't send that param, the undelying value will be $false by default
)
Then remove
Write-host ("`tLabName : {0}" -f $Lab.Name) -ForegroundColor Yellow
if ($null -ne $Lab) {
$LabToRemove = $Lab
}
Important part here is the ValueFromPipelineByPropertyName = $true declaration

Answer 2

begin runs before anything else, including pipeline parameter binding - so you need to move code that inspects a pipeline-bound parameter (like $Lab) to the process block:
Function Remove-Lab{
[CmdletBinding(DefaultParameterSetName='Lab')]
param (
[Parameter(ValueFromPipeline=$true,ParameterSetName='Lab',Position=0,Mandatory=$true)]
[Lab]
$Lab,
# Parameter help description
[Parameter(Position=1,Mandatory=$false)]
[switch]
$Force=$false
)
process {
Write-host ("`tLabName : {0}" -f $Lab.Name) -ForegroundColor Yellow
if ($null -ne $Lab) {
$LabToRemove = $Lab
}
if (-not [string]::IsNullOrEmpty($LabId)) {
$LabToRemove = Get-Lab -Id $LabId
}
if (-not [string]::IsNullOrEmpty($Name)) {
$LabToRemove = Get-Lab -Name $Name
}
if ($null -eq $LabToRemove) {
throw "There is no Lab with specified characteristics. Please check your input"
}
$DoRemoval = $true
if ($Force.IsPresent -eq $false) {
while ($null -eq $UserInput -or $UserInput -notin #('Y','N')) {
$UserInput = Read-HostDefault -Prompt "Are you sure want to remove the selected Lab and all its components ? [Y]es, [N]o" -Default 'N'
if ($UserInput -eq 'N') {
$DoRemoval = $false
}
}
Write-Host ("`tUser Input : {0}" -f $UserInput) -ForegroundColor Green
}
if ($DoRemoval -eq $true) {
Write-Host ("`tAbout to Remove the following Lab : {0}" -f $LabToRemove.Name) -ForegroundColor Green
}
}