PowerShell - Using Parameter Sets

💡 What are parameter sets in PowerShell and how to use them

Have you ever wondered when you are writing a PowerShell function or commandlet how you can make only certain parameters be presented to the consumer of the function in certain scenarios? That's where parameter sets come in. 😄

We will look at the following test function: [Test-ParameterSets] on exactly how this functionality can be used.

	Function Test-ParameterSets {
	[CmdletBinding(SupportsShouldProcess, DefaultParameterSetName="Default")]
	Param (
	[Parameter(Mandatory=$false)]
	[string]$DefaultParameter1,
	[Parameter(Mandatory=$false)]
	[string]$DefaultParameter2,
	[Parameter(Mandatory=$false, ParameterSetName="A")]
	[Switch]$A,
	[Parameter(Mandatory=$false, ParameterSetName="A")]
	[string]$AParameter1,
	[Parameter(Mandatory=$false, ParameterSetName="A")]
	[string]$AParameter2,
	[Parameter(Mandatory=$false, ParameterSetName="B")]
	[Switch]$B,
	[Parameter(Mandatory=$false, ParameterSetName="B")]
	[string]$BParameter1,
	[Parameter(Mandatory=$false, ParameterSetName="B")]
	[string]$BParameter2
	)
	If ($A) {
	Write-Output "Using Parameter Set A"
	Write-Output $DefaultParameter1
	Write-Output $DefaultParameter2
	Write-Output $AParameter1
	Write-Output $AParameter2
	}
	If ($B) {
	Write-Output "Using Parameter Set B"
	Write-Output $DefaultParameter1
	Write-Output $DefaultParameter2
	Write-Output $BParameter1
	Write-Output $BParameter2
	}
	}
	# Function Tests #
	Test-ParameterSets -DefaultParameter1 'defaultValue1' -DefaultParameter2 'defaultValue2' -A -AParameter1 'valueA1' -AParameter2 'valueA2'
	Test-ParameterSets -DefaultParameter1 'defaultValue1' -DefaultParameter2 'defaultValue2' -B -BParameter1 'valueB1' -BParameter2 'valueB2'

view raw PowerShell-Using-Parameter-Sets.ps1 hosted with ❤ by GitHub

The first step is to add a DefaultParameterSetName="Default". We can set that in our [CmdletBinding()] as follow:

// code/demo-function.ps1#L2-L2

[CmdletBinding(SupportsShouldProcess, DefaultParameterSetName="Default")]

By declaring a default parameter set name on our [CmdletBinding()] will set all of our parameters defined under the Default set. What we will do next is define which parameters needs to be presented if the parameter switch $A is used. We do not want to present parameters from switch $B in this case. We will do this by defining a new parameter set name and grouping the parameters we want to be part of that particular set.

// code/demo-function.ps1#L8-L13

[Parameter(Mandatory=$false, ParameterSetName="A")]
[Switch]$A,
[Parameter(Mandatory=$false, ParameterSetName="A")]
[string]$AParameter1,
[Parameter(Mandatory=$false, ParameterSetName="A")]
[string]$AParameter2,

We will also give parameter switch $B and it's corresponding parameters, it's own parameter set name.

// code/demo-function.ps1#L14-L19

[Parameter(Mandatory=$false, ParameterSetName="B")]
[Switch]$B,
[Parameter(Mandatory=$false, ParameterSetName="B")]
[string]$BParameter1,
[Parameter(Mandatory=$false, ParameterSetName="B")]
[string]$BParameter2

Now that we have defined our parameter sets and grouped the relevant parameters according to their sets our function/Cmdlet will now only present corresponding parameters based on which switch is used when calling the function/Cmdlet.

You can also find some very helpful documentation on parameter sets on Microsoft Docs.

I hope you have enjoyed this post and have learned something new. You can also find the code samples used in this blog post on my GitHub page. ❤️

Author

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Marcel.LFollow

Dual Microsoft MVP DevOps + Azure | DevOps Architect | Technical speaker focused on Microsoft technologies, IaC and automation in Azure. Find me on GitHub: https://github.com/Pwd9000-ML

Comments

[Chris Bergmeister]

Two suggestions:

• Mandatory property on parameters default to false, therefore you could make the code easier to read by just removing all the Mandatory=$false bits. As an aside: When adding the Mandatory attribute one doesn't even need to assign a value, one can do just [Parameter(Mandatory], which makes it nicer to read. docs.microsoft.com/en-us/dotnet/ap...
• Use .IsPresent property on switch parameters so that the person reading the code knows it's a switch paramter docs.microsoft.com/en-us/dotnet/ap...

[Marcel.L]

Those are awesome tips @cbergmeister Thank you!