Question

I don’t remember ever being prompted for multiple selections before in PowerShell, but I’ve seen several examples of hosts implementing this interface. Unfortunately, those are the only references I’ve seen to the interface. I’ve never seen “here’s how to test that you’re implementing it correctly”.

Answer 1

Please, disregard my first answer; it is not an answer at all, as I can see now. And thank you for a really interesting question.

I still do not know cmdlets that use that interface. But we can use it on our own from scripts. Let’s modify the mentioned Get-Choice.ps1 and call the new one Get-Choice2.ps1:

<#
.SYNOPSIS
    Displays PowerShell style menu and gets user choices

.DESCRIPTION
    *) Returns choice indexes.
    *) Choice keys are indicated by '&' in menu items.
    *) Help strings can be empty or nulls (items are used themselves).
#>

param
(
    # Menu caption
    [string]$Caption = 'Confirm',
    # Menu message
    [string]$Message = 'Are you sure you want to continue?',
    # Choice info pairs: item1, help1, item2, help2, ...
    [string[]]$Choices = ('&Yes', 'Continue', '&No', 'Stop'),
    # Default choice indexes (i.e. selected on [Enter])
    [int[]]$DefaultChoice = @(0)
)
if ($args) { throw "Unknown parameters: $args" }
if ($Choices.Count % 2) { throw "Choice count must be even." }

$descriptions = @()
for($i = 0; $i -lt $Choices.Count; $i += 2) {
    $c = [System.Management.Automation.Host.ChoiceDescription]$Choices[$i]
    $c.HelpMessage = $Choices[$i + 1]
    if (!$c.HelpMessage) {
        $c.HelpMessage = $Choices[$i].Replace('&', '')
    }
    $descriptions += $c
}

$Host.UI.PromptForChoice($Caption, $Message, [System.Management.Automation.Host.ChoiceDescription[]]$descriptions, $DefaultChoice)

Now we test it:

Get-Choice2 'Title' 'Message' -DefaultChoice 0, 1, 2 -Choices @(
    'Choice &1', 'This is choice 1'
    'Choice &2', ''
    'Choice &3', ''
    'Choice &4', ''
    'Choice &5', ''
    'Choice &6', ''
    'Choice &7', ''
    'Choice &8', ''
    'Choice &9', ''
    'Choice &0', ''
)

It prints 10 choices, the first 3 are highlighted (in the console host), and prompts:

0> Test-Get-Choice2.ps1
Title
Message
[1] Choice 1
[2] Choice 2
[3] Choice 3
[4] Choice 4
[5] Choice 5
[6] Choice 6
[7] Choice 7
[8] Choice 8
[9] Choice 9
[0] Choice 0
[?] Help
(default choices are 1,2,3)
Choice[0]:

If we press Enter immediately the output is the default 3 indexes: 0, 1, 2. If we type, for example: 5 + Enter + 3 + Enter + 1 + Enter + Enter then the output is 4, 2, 0.

It works. PowerShell ISE also supports this but the UI might be something better in GUI version, perhaps.