Powershell parameter sets, how to get one parameter from each set but not both?

Question

I am trying to write what seems very simple but I've been going at this for hours and still not able to get what I need.

I have a PowerShell script which will be used for starting up OR shutting down virtual machines. I want to user to specify either a ResourceGroup name, an individual VM name or a text file with the names of the VMs.

This script is used for Azure but the question is specific to the param() declaration.

I have tried every combination I can think of here, making parameters parts of parameter sets, making them mandatory, not mandatory, etc. but I have not been able to get this right.

Any help is appreciated!

param (
    [Parameter (Mandatory = $true, ParameterSetName = 'ByResourceGroup')]
    [string]$ResourceGroup,

    [Parameter (Mandatory = $true, ParameterSetName = 'ByFile')]
    [string]$File,

    [Parameter (Mandatory = $true, ParameterSetName = 'ByName')]
    [string]$Name,

    [Parameter (Mandatory = $false, ParameterSetName = 'ByResourceGroup')]
    [Parameter (Mandatory = $false, ParameterSetName = 'ByFile')]
    [Parameter (Mandatory = $false, ParameterSetName = 'ByName')]
    [switch]$Start,

    [Parameter (Mandatory = $false, ParameterSetName = 'ByResourceGroup')]
    [Parameter (Mandatory = $false, ParameterSetName = 'ByFile')]
    [Parameter (Mandatory = $false, ParameterSetName = 'ByName')]
    [switch]$Stop
)

The user should be able to pass in EITHER: -ResourceGroup OR -File OR -Name

AND

pass in either: -Start OR -Stop

Not both!

I think I have this correct for the first set but I can't get the -Start and -Stop to be exclusive.

Get-help says this:

SYNTAX
    C:\Set-AzureVM.ps1 -ResourceGroup <String> [-Start] [-Stop] [<CommonParameters>]

    C:\Set-AzureVM.ps1 -File <String> [-Start] [-Stop] [<CommonParameters>]

    C:\Set-AzureVM.ps1 -Name <String> [-Start] [-Stop] [<CommonParameters>]


I am looking for something more like this:

SYNTAX
    C:\Set-AzureVM.ps1 -ResourceGroup <String> -Start [<CommonParameters>]

    C:\Set-AzureVM.ps1 -File <String> -Start [<CommonParameters>]

    C:\Set-AzureVM.ps1 -Name <String> -Start [<CommonParameters>]

    C:\Set-AzureVM.ps1 -ResourceGroup <String> -Stop [<CommonParameters>]

    C:\Set-AzureVM.ps1 -File <String> -Stop [<CommonParameters>]

    C:\Set-AzureVM.ps1 -Name <String> -Stop [<CommonParameters>]

Just to close this out... I wound up changing this a bit (needs changed and so did the code). As others suggested, I agree that what I was trying to do probably wasn't possible anyway. Also, I am handling the possibility that the user will choose both -Start and -Stop or neither in code. Thanks to everyone for your comments!

SYNTAX
    C:\Set-AzureVM.ps1 -Name <String> -ResourceGroup <String> [-Start] [-Stop] [<CommonParameters>]

    C:\Set-AzureVM.ps1 -File <String> [-Start] [-Stop] [<CommonParameters>]

I would personally just have a single switch with a ValidateSet('Stop','Start'). You can also just have both with logic in the script that handles the discrepancy. I feel you can't do what you want with the number of parameters you have. — AdminOfThings
– AdminOfThings, Commented Jul 8, 2019 at 16:41

Jakobii · Accepted Answer · 2019-07-08 18:21:12Z

2

I don't think what you are trying to do is possible. You might consider breaking the functionality up into two separate scripts.

Start-AzureVM.ps1
Stop-AzureVM.ps1

Alternatively you can use the switch -stop to do both starting and stopping. by default -stop will evaluate to $false in your script or function.

# implicitly start the vm
Set-AzureVM.ps1 -Name <String>

# explicitly stop the vm
Set-AzureVM.ps1 -Name <String> -stop

function Set-AzureVM () {
    param(
        [Parameter (Mandatory, ParameterSetName = 'ByFile')]
        [string]$File,

        [Parameter (Mandatory, ParameterSetName = 'ByName')]
        [string]$Name,

        [switch]$Stop
    )
    if($Stop){
        Write-Host 'Stopping VM'
    }
    if(!$stop){
        Write-Host 'Starting VM'
    }
}

Get-Command Set-AzureVM -Syntax

Set-AzureVM -File <string> [-Stop] [<CommonParameters>]

Set-AzureVM -Name <string> [-Stop] [<CommonParameters>]

answered Jul 8, 2019 at 18:21

Jakobii

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1 Comment

RichardF Over a year ago

Thanks for your suggestions. FYI, the code was originally in two different scripts but the work item acceptance criteria was for one script.

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