Dynamically define dynamic parameters for Powershell functions

dynamic-dynamic-params.ps1

function Verb-Noun {
    [CmdletBinding()]
    param (
        # a normal parameter
        [Parameter(ValueFromPipeline = $true)]
        [System.String]$Name, 
    )
    dynamicparam {
        # a simple dynamic parameter, $PossibleCategories is discovered on module import
        $DynamicParams        = New-Object System.Management.Automation.RuntimeDefinedParameterDictionary
        $Param1               = New-Object System.Management.Automation.RuntimeDefinedParameter
        $Param1Attr           = New-Object System.Management.Automation.ParameterAttribute
        $Param1Validation     = New-Object System.Management.Automation.ValidateSetAttribute -ArgumentList ($PossibleCategories | Select-Object -ExpandProperty Name)
        $Param1.Name          = 'CategoryName'
        $Param1.ParameterType = [System.String]
        $Param1Attr.Mandatory = $true
        
        $Param1.Attributes.Add($Param1Attr)
        $Param1.Attributes.Add($Param1Validation)
        $DynamicParams.Add('CategoryName', $Param1)

        # dynamically defined dynamic params, $PossibleAttributesHash again discovered on module import
        $Script:PossibleAttributesHash.GetEnumerator() | ForEach-Object {
            $Param1               = New-Object System.Management.Automation.RuntimeDefinedParameter
            $Param1Attr           = New-Object System.Management.Automation.ParameterAttribute
            $Param1Validation     = New-Object System.Management.Automation.ValidateSetAttribute -ArgumentList $Script:PossibleAttributesHash[$_.Key]
            $Param1.Name          = $_.Key
            $Param1.ParameterType = [System.String]
            
            #when adding a new machine site is manatory
            if ($_.Key -in 'site') {
                $Param1Attr.Mandatory = $true
            } else {
                $Param1Attr.Mandatory = $false
            }
            
            $Param1.Attributes.Add($Param1Attr)
            $Param1.Attributes.Add($Param1Validation)
            $DynamicParams.Add($_.Key, $Param1)
        }

        Return $DynamicParams
    }
    begin {}
    process {}
    end {}
}