Make parameter mandatory based on switch - PowerShell

Question

I was struggling in a situation where I need to make some parameters mandatory ONLY if a switch or combination of switches is used. Below is the example of what I am trying to do:

[CmdletBinding(DefaultParameterSetName='DefaultConfiguration')]
Param
(        
[Parameter(Mandatory=$true)][String]$Location,
[Parameter(Mandatory=$true)][String]$DPMServername,

[Parameter(Mandatory=$False, ParameterSetName='CustomConfiguration')]
[Switch]$CustomizeDPMSubscriptionSettings,
[Parameter(Mandatory=$True, ParameterSetName='CustomConfiguration')]
[String]$StagingAreaPath,

[Parameter(Mandatory=$False, ParameterSetName='EncryptionSettings')]
[Parameter(ParameterSetName='CustomConfiguration')]
[Switch]$SetEncryption,
[Parameter(Mandatory=$true, ParameterSetName='EncryptionSettings')]
[Parameter(Mandatory=$False, ParameterSetName='CustomConfiguration')]
[String]$EncryptionPassPhrase,

[Parameter(Mandatory=$False, ParameterSetName='ProxyEnabled')]
[Parameter(ParameterSetName='CustomConfiguration')]
[Switch]$SetProxy,
[Parameter(Mandatory=$true, ParameterSetName='ProxyEnabled')]
[Parameter(ParameterSetName='CustomConfiguration')]
[String]$ProxyServerAddress,
[Parameter(Mandatory=$true, ParameterSetName='ProxyEnabled')]
[Parameter(Mandatory=$False, ParameterSetName='CustomConfiguration')]
[String]$ProxyServerPort
)

Here, I need to follow below conditions:

1. If -CustomizeDPMSubscriptionSettings (Switch) parameter is used, it must ask for the Staging AreaPath ---- This is Working fine
2. ONLY when -CustomizeDPMSubscriptionSettings (Switch) parameter is used with -SetEncryption, it must ask for -EncryptionPassPhrase
3. And ONLY when -CustomizeDPMSubscriptionSettings (Switch) parameter is used with -SetProxy, it must ask for -ProxyServerAddress and -ProxyServerPort

Sorry if this sounds like a repeated question but other posts I found here are not helping me solve my issue. I am confused :-(

NOTE: Above code is part of what I was trying with different combinations. Please correct as necessary.

Answer 1

Here is a solution that seems to do what you expect.
What I did was create a parameter set for each possible combination.
- CustomConfiguration
- EncryptionSettings
- ProxyEnabled
- EncryptionAndProxy

One limitation is that it will not prompt for specific missing parameters unless using EncryptionAndProxy, but will instead state that it cannot resolve the parameter set.

[CmdletBinding(DefaultParameterSetName='DefaultConfiguration')]
Param
(        
[Parameter(Mandatory=$true)][String]$Location,
[Parameter(Mandatory=$true)][String]$DPMServername,

[Parameter(Mandatory=$True, ParameterSetName='CustomConfiguration')]
[Parameter(Mandatory=$True, ParameterSetName='EncryptionSettings')]
[Parameter(Mandatory=$True, ParameterSetName='ProxyEnabled')]
[Parameter(Mandatory=$True, ParameterSetName='EncryptionAndProxy')]
[Switch]$CustomizeDPMSubscriptionSettings,

[Parameter(Mandatory=$True, ParameterSetName='CustomConfiguration')]
[Parameter(Mandatory=$True, ParameterSetName='EncryptionSettings')]
[Parameter(Mandatory=$True, ParameterSetName='ProxyEnabled')]
[Parameter(Mandatory=$True, ParameterSetName='EncryptionAndProxy')]
[String]$StagingAreaPath,

[Parameter(Mandatory=$True, ParameterSetName='EncryptionSettings')]
[Parameter(Mandatory=$True, ParameterSetName='EncryptionAndProxy')]
[Switch]$SetEncryption,

[Parameter(Mandatory=$true, ParameterSetName='EncryptionSettings')]
[Parameter(Mandatory=$True, ParameterSetName='EncryptionAndProxy')]
[String]$EncryptionPassPhrase,

[Parameter(Mandatory=$True, ParameterSetName='ProxyEnabled')]
[Parameter(Mandatory=$True, ParameterSetName='EncryptionAndProxy')]
[Switch]$SetProxy,

[Parameter(Mandatory=$true, ParameterSetName='ProxyEnabled')]
[Parameter(Mandatory=$True, ParameterSetName='EncryptionAndProxy')]
[String]$ProxyServerAddress,

[Parameter(Mandatory=$true, ParameterSetName='ProxyEnabled')]
[Parameter(Mandatory=$True, ParameterSetName='EncryptionAndProxy')]
[String]$ProxyServerPort
)

I'm looking into a second potential solution based on dynamic parameters.

Edit: As promised, here's a solution based on dynamic parameters

[CmdletBinding(DefaultParameterSetName='DefaultConfiguration')]
Param
(        
    [Parameter(Mandatory=$true)][String]$Location,
    [Parameter(Mandatory=$true)][String]$DPMServername,

    [Switch]$CustomizeDPMSubscriptionSettings,
    [Switch]$SetEncryption,
    [Switch]$SetProxy
)

DynamicParam
{
    $paramDictionary = New-Object -Type System.Management.Automation.RuntimeDefinedParameterDictionary
    $attributes = New-Object System.Management.Automation.ParameterAttribute
    $attributes.ParameterSetName = "__AllParameterSets"
    $attributes.Mandatory = $true
    $attributeCollection = New-Object -Type System.Collections.ObjectModel.Collection[System.Attribute]
    $attributeCollection.Add($attributes)
    # If "-SetEncryption" is used, then add the "EncryptionPassPhrase" parameter
    if($SetEncryption)
    { 
        $dynParam1 = New-Object -Type System.Management.Automation.RuntimeDefinedParameter("EncryptionPassPhrase", [String], $attributeCollection)   
        $paramDictionary.Add("EncryptionPassPhrase", $dynParam1)
    }
    # If "-SetProxy" is used, then add the "ProxyServerAddress" "ProxyServerPort" and parameters
    if($SetProxy)
    {
        $dynParam1 = New-Object -Type System.Management.Automation.RuntimeDefinedParameter("ProxyServerAddress", [String], $attributeCollection)   
        $paramDictionary.Add("ProxyServerAddress", $dynParam1)
        $dynParam2 = New-Object -Type System.Management.Automation.RuntimeDefinedParameter("ProxyServerPort", [String], $attributeCollection)   
        $paramDictionary.Add("ProxyServerPort", $dynParam2)
    }
    # If "-CustomizeDPMSubscriptionSettings" is used, then add the "StagingAreaPath" parameter
    if($CustomizeDPMSubscriptionSettings)
    {
        $dynParam1 = New-Object -Type System.Management.Automation.RuntimeDefinedParameter("StagingAreaPath", [String], $attributeCollection)   
        $paramDictionary.Add("StagingAreaPath", $dynParam1)
    }
    return $paramDictionary
}
Process{
    foreach($key in $PSBoundParameters.keys)
    {
        Set-Variable -Name $key -Value $PSBoundParameters."$key" -Scope 0
    }
}

What this one does is dynamically add parameters to your function based on the presence of each switch.
This supports autocompletion, and has better support for missing parameters. It will explicitly ask for missing parameters if the corresponding switch is used.
Second edit: I added the Process section that's mandatory with this construct, as well as the variable creation bit, which makes things much easier.