PowerShell
Parámetros dinámicos de PowerShell

Parámetro dinámico "simple"

Este ejemplo agrega un nuevo parámetro a MyTestFunction si $SomeUsefulNumber es mayor que 5.

function MyTestFunction
{
    [CmdletBinding(DefaultParameterSetName='DefaultConfiguration')]
    Param
    (
        [Parameter(Mandatory=$true)][int]$SomeUsefulNumber
    )

    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 "SomeUsefulNumber" is greater than 5, then add the "MandatoryParam1" parameter
        if($SomeUsefulNumber -gt 5)
        {
            # Create a mandatory string parameter called "MandatoryParam1"
            $dynParam1 = New-Object -Type System.Management.Automation.RuntimeDefinedParameter("MandatoryParam1", [String], $attributeCollection)   
            # Add the new parameter to the dictionary
            $paramDictionary.Add("MandatoryParam1", $dynParam1)
        }
        return $paramDictionary
    }

    process
    {
        Write-Host "SomeUsefulNumber = $SomeUsefulNumber"
        # Notice that dynamic parameters need a specific syntax
        Write-Host ("MandatoryParam1 = {0}" -f $PSBoundParameters.MandatoryParam1)
    }

}

Uso:

PS >  MyTestFunction -SomeUsefulNumber 3
SomeUsefulNumber = 3
MandatoryParam1 =

PS >  MyTestFunction -SomeUsefulNumber 6
cmdlet MyTestFunction at command pipeline position 1
Supply values for the following parameters:
MandatoryParam1:

PS >MyTestFunction -SomeUsefulNumber 6 -MandatoryParam1 test
SomeUsefulNumber = 6
MandatoryParam1 = test

En el segundo ejemplo de uso, puede ver claramente que falta un parámetro.

Los parámetros dinámicos también se tienen en cuenta con la finalización automática.
Esto es lo que sucede si presionas ctrl + espacio al final de la línea:

PS >MyTestFunction -SomeUsefulNumber 3 -<ctrl+space>
Verbose              WarningAction        WarningVariable      OutBuffer
Debug                InformationAction    InformationVariable  PipelineVariable
ErrorAction          ErrorVariable        OutVariable

PS >MyTestFunction -SomeUsefulNumber 6 -<ctrl+space>
MandatoryParam1      ErrorAction          ErrorVariable        OutVariable
Verbose              WarningAction        WarningVariable      OutBuffer
Debug                InformationAction    InformationVariable  PipelineVariable