LINQ SelectMany for PowerShell

ArrayMap.ps1

SelectMany -Source (1,2),(3,4) {$Source | %{"OU={0}" -f $_}} -Verbose

<#
詳細: 1 2
詳細: OU=1 OU=2
OU=1
OU=2
詳細: 3 4
詳細: OU=3 OU=4
OU=3
OU=4
#>

SelectMany -Source (1,2),(3,4)

<#
1
2
3
4
#>

SelectMany -Source (1,2),(3,4) | measure

<#
Count    : 4
#>

Input.ps1

SelectMany -Source 1,2,(3,4) {$Source | %{"OU={0}" -f $_}} -Verbose

<#
詳細: 1
詳細: OU=1
OU=1
詳細: 2
詳細: OU=2
OU=2
詳細: 3 4
詳細: OU=3 OU=4
OU=3
OU=4
#>

Pipeline.ps1

1,2,(3,4) | SelectMany -ScriptBlock {$Source | %{"OU={0}" -f $_}} -Verbose

<#
詳細: 1
詳細: OU=1
OU=1
詳細: 2
詳細: OU=2
OU=2
詳細: 3
詳細: OU=3
OU=3
詳細: 4
詳細: OU=4
OU=4
#>

SelectMany.ps1

#Requires -Version 4.0
function SelectMany 
{
    [CmdletBinding()]
    param
    (
        [parameter(Mandatory = 1, Position = 0, ValueFromPipeline = 1)]
        [PSObject[]]$Source,

        [parameter(Mandatory = 0, Position = 1)]
        [ScriptBlock]$ScriptBlock = {$Source}
    )
    
    process
    {
        foreach ($x in $Source)
        {
            $output = $ScriptBlock.GetNewClosure().InvokeWithContext(
                $null,
                (New-Object "System.Management.Automation.PSVariable" ("Source", $x))
            )
            foreach ($o in $output)
            {
                $o
            }
        }
    }
}