What is the simplest form of Dynamic Parameters?-CodePudding

Trying to get a better understanding of Dynamic Parameters, but something keeps bothering me. All examples I've found across the outer-webs (internet), the parameter attributes are always defined/included.

Here's what I'm working with:

Function Test-DynamicParameters {
[cmdletbinding()]
    Param (
        [System.IO.DirectoryInfo]$Path
    )
    DynamicParam
    {
        if ($Path.Extension) {
              $parameterAttribute = [System.Management.Automation.ParameterAttribute]@{
                  Mandatory = $false
              }

              $attributeCollection = [System.Collections.ObjectModel.Collection[System.Attribute]]::new()
              $attributeCollection.Add($parameterAttribute)

              $dynParam1 = [System.Management.Automation.RuntimeDefinedParameter]::new(
                'TestSwitch', [switch], $attributeCollection
              )

              $paramDictionary = [System.Management.Automation.RuntimeDefinedParameterDictionary]::new()
              $paramDictionary.Add('TestSwitch', $dynParam1)
              $paramDictionary
        }
    }
    Begin { }
    Process
    {
        $PSBoundParameters
    }
    End { }
}

. . .currently have tried numerous combinations of removing certain lines/code to see what would make my Dynamic Parameter show, but nothing works without the attributes being declared. Is this necessary?

Question: what is the simplest form of Dynamic Parameter declaration that I would need for it to work?

For Example - can it just be shortened to where I only define just the name? Or, would PowerShell insist a type is specified instead of defaulting to [object]? Something like:

$paramDictionary = [System.Management.Automation.RuntimeDefinedParameterDictionary]::new()
$paramDictionary.Add('TestSwitch')
$paramDictionary

CodePudding user response：

What kind of behavior are you looking for? Because dynamic parameters are usually not needed, even if the auto-completion is dynamic.

For example you could do

autocomplete module names for Get-Command -Module
or search for files by filetype, only complete filetypes if they exist in that directory

Windows Powershell

You can use DynamicValidateSet pattern in WindowsPowershell

gif using DynamicValidateSet

New in PowerShell

6 adds Suggestions

New: [IValidateSetValuesGenerator] and [ArgumentCompletions]

It autocompletes like [ValidateSet], but the user is still free to enter others.

Note, [ArgumentCompletions] and [ArgumentCompleter] are two different classes.

[Parameter(Mandatory)]
[ArgumentCompletions('Fruits', 'Vegetables')]
[string]$Type,

7.2 Generic Completers

New [ArgumentCompleter] attribute with the [IArgumentCompleterFactory] interface

from the docs:

[DirectoryCompleter(ContainingFile="pswh.exe", Depth=2)]

[DateCompleter(WeekDay='Monday', From="LastYear")]

[GitCommits(Branch='release')]

CodePudding user response：

You can’t as the function add of the type System.Management.Automation.RuntimeDefinedParameterDictionary require to provide a key and value which is exactly a String (key) and a System::Management::Automation::RuntimeDefinedParameter for the value. For more information you can check the class documentation here https://docs.microsoft.com/en-us/dotnet/api/system.management.automation.runtimedefinedparameterdictionary?view=powershellsdk-7.0.0. I have tested on my side and you need at least the ParameterAttribute Mandatory set to true in order to make it run, and the key/name used in the RuntimeDefinedParameter must match the key used in the dictionnary when you add it. So the minimum code that you need should be like this:

       Function Test-DynamicParameters {
[cmdletbinding()]
    Param (
        [System.IO.FileSystemInfo ]$Path
    )
    DynamicParam
    {
        if ($Path.Extension) {
              $parameterAttribute = [System.Management.Automation.ParameterAttribute]@{
               Mandatory = $true
              }

              $attributeCollection = [System.Collections.ObjectModel.Collection[System.Attribute]]::new()
              $attributeCollection.Add($parameterAttribute)

              $dynParam1 = [System.Management.Automation.RuntimeDefinedParameter]::new("TestSwitch", [string], $attributeCollection)

              $paramDictionary = [System.Management.Automation.RuntimeDefinedParameterDictionary]::new()
              $paramDictionary.Add('TestSwitch', $dynParam1)
              $paramDictionary
        }
    }
    Begin { }
    Process
    {
        $PSBoundParameters
    }
    End { }
}
$FileNamePath = "C:\tmp\stackoverflow\test.txt";
$path = (Get-Item $FileNamePath )
Test-DynamicParameters -Path $path