Auto Populating a Parameters’ Value from a Dynamic List

First off, I want to give a shout out to Author: Martin Schvartzman and his blog posting https://blogs.technet.microsoft.com/pstips/2014/06/09/dynamic-validateset-in-a-dynamic-parameter/.

A question that I often get when teaching parameter validation is "can you load the values of a parameter dynamically?" Up until now, my answer was no.  Time to change that.  After getting that question again, I did some more research and found Martin’s article.  Simply adjusting 1 line of the code from his blog posting allowed me to load the SamAccountNames of all users in the domain as the valid, and TAB complete capable, values of a parameter.  Below is that code:

# Author: Martin Schvartzman

# https://blogs.technet.microsoft.com/pstips/2014/06/09/dynamic-validateset-in-a-dynamic-parameter/

# Minor modifications: Jason Yoder

function Test-DynamicValidateSet {

    [CmdletBinding()]

    Param(

        # Any other parameters can go here

    )

    DynamicParam {

            # Set the dynamic parameters' name

            $ParameterName = 'User'

           

            # Create the dictionary

            $RuntimeParameterDictionary = New-Object System.Management.Automation.RuntimeDefinedParameterDictionary

            # Create the collection of attributes

            $AttributeCollection = New-Object System.Collections.ObjectModel.Collection[System.Attribute]

           

            # Create and set the parameters' attributes

            $ParameterAttribute = New-Object System.Management.Automation.ParameterAttribute

            $ParameterAttribute.Mandatory = $true

            $ParameterAttribute.Position = 1

            # Add the attributes to the attributes collection

            $AttributeCollection.Add($ParameterAttribute)

            # Generate and set the ValidateSet.

            # Change the next line to produce what you want to auto populate for the parameter.

            # Make sure it is DataType String.

            $arrSet = Get-ADUser -Filter * | Select-Object -ExpandProperty SamAccountName

            $ValidateSetAttribute = New-Object System.Management.Automation.ValidateSetAttribute($arrSet)

            # Add the ValidateSet to the attributes collection

            $AttributeCollection.Add($ValidateSetAttribute)

            # Create and return the dynamic parameter

            $RuntimeParameter = New-Object System.Management.Automation.RuntimeDefinedParameter($ParameterName, [string], $AttributeCollection)

            $RuntimeParameterDictionary.Add($ParameterName, $RuntimeParameter)

            return $RuntimeParameterDictionary

    }

    begin {

        # Bind the parameter to a friendly variable

        $User = $PsBoundParameters[$ParameterName]

    }

    process {

        # Your code goes here

        Get-ADUser -Identity $USer

    }

}