How do you support PowerShell's -WhatIf & -Confirm parameters in a Cmdlet that calls other Cmdlets?

Question

I have a PowerShell script cmdlet that supports the -WhatIf & -Confirm parameters.

It does this by calling the $PSCmdlet.ShouldProcess() method before performing the change.
This works as expected.

The problem I have is that my Cmdlet is implemented by calling other Cmdlets and the -WhatIf or -Confirm parameters are not passed along to the Cmdlets I invoke.

How can I pass along the values of -WhatIf and -Confirm to the Cmdlets I call from my Cmdlet?

For example, if my Cmdlet is Stop-CompanyXyzServices and it uses Stop-Service to implement its action.

If -WhatIf is passed to Stop-CompanyXyzServices I want it to also be passed to Stop-Service.

Is this possible?

Answer 1

After some googling I came up with a good solution for passing common parameters along to called commands. You can use the @ splatting operator to pass along all the parameters that were passed to your command. For example, if

Start-Service -Name ServiceAbc @PSBoundParameters

is in the body of your script powershell will pass all the parameters that were passed to your script to the Start-Service command. The only problem is that if your script contains say a -Name parameter it will be passed too and PowerShell will complain that you included the -Name parameter twice. I wrote the following function to copy all the common parameters to a new dictionary and then I splat that.

function Select-BoundCommonParameters
{
    [CmdletBinding()]
    param(
        [Parameter(Mandatory=$true)]
        $BoundParameters
    )
    begin
    {
        $boundCommonParameters = New-Object -TypeName 'System.Collections.Generic.Dictionary[string, [Object]]'
    }
    process
    {
        $BoundParameters.GetEnumerator() |
            Where-Object { $_.Key -match 'Debug|ErrorAction|ErrorVariable|WarningAction|WarningVariable|Verbose' } |
            ForEach-Object { $boundCommonParameters.Add($_.Key, $_.Value) }

        $boundCommonParameters
    }
}

The end result is you pass parameters like -Verbose along to the commands called in your script and they honor the callers intention.