PowerShell function to create runtime defined dynamic parameters.

New-RuntimeDefinedParameter.ps1

#Requires -PSEdition Core
using namespace System;
using namespace System.IO;
using namespace System.Reflection;
using namespace System.Collections.Generic;
using namespace System.Management.Automation;
using namespace System.Management.Automation.Language;
using namespace System.Collections.ObjectModel;

function New-RuntimeDefinedParameter {
    <# 
    .SYNOPSIS
    Simplifies defining runtime Parameters for a function.
    .DESCRIPTION 
    Instead of many lines of code for each Parameter defined in the DynamicParam block of an Advanced function, this function can be used to define each runtime Parameter in 1-2 lines of code.

    Microsoft Learn Example of defining one runtime Parameter:
        $ParameterAttribute = [System.Management.Automation.ParameterAttribute]@{
                ParameterSetName = "ByRegistryPath"
                Mandatory = $false
            }
            $AttributeCollection = [System.Collections.ObjectModel.Collection[System.Attribute]]::new()
            $AttributeCollection.Add($ParameterAttribute)
            $dynParam1 = [System.Management.Automation.RuntimeDefinedParameter]::new(
            'KeyCount', [Int32], $AttributeCollection
            )
            $ParamDictionary = [System.Management.Automation.RuntimeDefinedParameterDictionary]::new()
            $ParamDictionary.Add('KeyCount', $dynParam1)
        return $ParamDictionary

    Simplified version using this function:
            $RuntimeParamDictionary = [RuntimeDefinedParameterDictionary]::new()
            $RuntimeParamDictionary.Add('$KeyCount', $(New-RuntimeDefinedParameter -ParameterName 'KeyCount' -ParameterTypeName [int] -ParameterSetName "ByRegistryPath"))
        return $RuntimeParamDictionary

    .PARAMETER ParameterName
    The ParameterName argument specifies the name of runtime Parameter that is returned by the function.
    .PARAMETER ParameterTypeName
    The ParameterTypeName argument specifies the name of runtime Parameter that is returned by the function.
    .PARAMETER ParameterSetName
    The ParameterSetName argument specifies the Parameter set a runtime Parameter belongs to.
    .PARAMETER Attributes
    A list of Attributes to add to the runtime Parameter. You you must surround your expression with '()' if defining the Attributes in line. Attributes could include Alias, Validation, etc.
    .PARAMETER HelpMessage
    The HelpMessage argument specifies a string that contains a brief description of the runtime Parameter or its value.
    .PARAMETER HelpMessageBaseName
    Specifies the location where resource identifiers reside for the runtime defined Parameter localized help.
    .PARAMETER HelpMessageResourceId
    Specifies the resource identifier for a help message.
    .PARAMETER Position
    The Position argument determines whether the runtime Parameter name is required when the Parameter is used in a command.
    .PARAMETER Mandatory
    The Mandatory argument indicates that the runtime Parameter is required.
    .PARAMETER ValueFromPipeline
    The ValueFromPipeline argument indicates that the runtime Parameter accepts input from a pipeline object. 
    .PARAMETER ValueFromPipelineByPropertyName
    The ValueFromPipelineByPropertyName argument indicates that the runtime Parameter accepts input from a property of a pipeline object.
    .PARAMETER ValueFromRemainingArguments
    The ValueFromRemainingArguments argument indicates that the runtime Parameter accepts all the Parameter's values in the command that aren't assigned to other Parameters of the function.
    .PARAMETER DontShow
    The DontShow argument indicates that the runtime Parameter will be hidden.
    .EXAMPLE
    DynamicParam {
        if(<SomeCondition>) {
                $RuntimeParamDictionary = [RuntimeDefinedParameterDictionary]::new()
                $RuntimeParamDictionary.Add('MyParam', $(New-RuntimeDefinedParameter -ParameterName 'MyParam' -ParameterTypeName [string] -ValueFromPipelineByPropertyName -ParameterSetName "Paramset1"))
            return $RuntimeParamDictionary
        }
    }
    .EXAMPLE
    DynamicParam {
        # You can also define validation Attributes on the RuntimeDefinedParameter

        switch ($Condition)
        Condition1 
        {
            $RuntimeParamDictionary = [RuntimeDefinedParameterDictionary]::new()
            $RuntimeParamDictionary.Add('MyParam', $(New-RuntimeDefinedParameter -ParameterName 'MyParam' -ParameterTypeName [string] -ValueFromPipelineByPropertyName -ParameterSetName "Paramset1"))
            
            return $RuntimeParamDictionary
        }
    }
    .LINK 
    https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_functions_advanced_Parameters?view=powershell-7.3#dynamic-Parameters
#>
    [CmdletBinding(PositionalBinding = $false)]
    [OutputType([RuntimeDefinedParameter])]
    Param (
        [Parameter(Mandatory, ValueFromPipelineByPropertyName)][ValidateNotNullOrEmpty()][string]$ParameterName,
        [Parameter(Mandatory, ValueFromPipelineByPropertyName)][ValidateNotNullOrEmpty()][PSTypeName]$ParameterTypeName,
        [Parameter(ValueFromPipelineByPropertyName)][ValidateNotNullOrEmpty()]$Value,
        [Parameter(ValueFromPipelineByPropertyName)][ValidateNotNullOrEmpty()][switch]$IsSet,
        [Parameter(ValueFromPipelineByPropertyName)][ValidateNotNullOrEmpty()][Attribute[]]$Attributes,
        [Parameter(ValueFromPipelineByPropertyName)][ValidateNotNullOrEmpty()][string]$ParameterSetName,
        [Parameter(ValueFromPipelineByPropertyName)][ValidateNotNullOrEmpty()][string]$HelpMessage,
        [Parameter(ValueFromPipelineByPropertyName)][ValidateNotNullOrEmpty()][string]$HelpMessageBaseName,
        [Parameter(ValueFromPipelineByPropertyName)][ValidateNotNullOrEmpty()][string]$HelpMessageResourceId,
        [Parameter(ValueFromPipelineByPropertyName)][ValidateScript({ $_ -ge 0 })][int]$Position,
        # [Parameter(ValueFromPipelineByPropertyName)][ValidateNotNullOrEmpty()][string]$ExperimentName,
        # [Parameter(ValueFromPipelineByPropertyName)][ValidateSet([ExperimentActionOptions])][string]$ExperimentAction,
        [Parameter(ValueFromPipelineByPropertyName)][switch]$Mandatory,
        [Parameter(ValueFromPipelineByPropertyName)][switch]$ValueFromPipeline,
        [Parameter(ValueFromPipelineByPropertyName)][switch]$ValueFromPipelineByPropertyName,
        [Parameter(ValueFromPipelineByPropertyName)][switch]$ValueFromRemainingArguments,
        [Parameter(ValueFromPipelineByPropertyName)][switch]$DontShow
    )
    Begin {
        $ParameterAttributes = [ParameterAttribute]::new()
    }
    Process {
        try {
            foreach ($Param in $PSBoundParameters.Keys) {
                if (-not ($Param.Equals("ParameterName") -or $Param.Equals("ParameterTypeName") -or $Param.Equals("Value") -or $Param.Equals("Attributes"))) {
                    $ParameterAttributes.$Param = $PSBoundParameters.$Param
                }
            }
            $RuntimeParam = [RuntimeDefinedParameter]@{
                Name = $ParameterName
                ParameterType = $ParameterTypeName.Type
                Value = $Value
                IsSet = $IsSet
            }
            $RuntimeParam.Attributes.Add($ParameterAttributes)
            foreach ($Attribute in $Attributes) {
                $RuntimeParam.Attributes.Add($Attribute)
            }
        }
        catch {
            Write-Error $_
        }
    }
    End {
        return $RuntimeParam
    }
}

# Class ExperimentActionOptions : IValidateSetValuesGenerator {
#     [string[]] GetValidValues () {
#         $ExperimentActions = [ExperimentAction].GetEnumValues()
#         return [string[]]$ExperimentActions
#     }
# }