Mutually exclusive parameters in PowerShell functions use the "ParameterSetName" attribute to assign parameters to different parameter sets (or groups of parameters).
A little known fact is that you can assign multiple parameter set names to one parameter. This way, a parameter could be optional in one scenario, and mandatory in another.
function Test-ParameterSet { [CmdletBinding(DefaultParameterSetName='NonCredential')] param ( $id, [Parameter(ParameterSetName='LocalOnly', Mandatory=$false)] $LocalAction, [Parameter(ParameterSetName='Credential', Mandatory=$true)] [Parameter(ParameterSetName='NonCredential', Mandatory=$false)] $ComputerName, [Parameter(ParameterSetName='Credential', Mandatory=$false)] $Credential ) $PSCmdlet.ParameterSetName $PSBoundParameters if ($PSBoundParameters.ContainsKey('ComputerName')) { Write-Warning 'Remote Call!' } }
The function Test-ParameterSet shows how to do this: -ComputerName is optional when the parameter set "NonCredential" is active. If a user uses the -Credential parameter, -ComputerName becomes mandatory. And if the user picks the -LocalAction parameter, neither -ComputerName nor -Credential is available anymore.
