https://qiita.com/acuo/items/9928e1fbb31b238d9705#%E4%BB%8A%E5%9B%9E%E4%BD%BF%E3%81%A3%E3%81%9F%E3%82%B3%E3%83%BC%E3%83%89%E5%85%A8%E3%81%A6

Measure.ps1

# https://qiita.com/acuo/items/9928e1fbb31b238d9705#%E4%BB%8A%E5%9B%9E%E4%BD%BF%E3%81%A3%E3%81%9F%E3%82%B3%E3%83%BC%E3%83%89%E5%85%A8%E3%81%A6

function Test($Scripts, $N) {
    # 各スクリプトの並びをシャッフルしてN回試行しその平均タイムを取得
    $Scripts * $N | Sort-Object { Get-random } |
    Select-Object Name, @{ name = "Time"; expression = { (Measure-Command $_.Script).TotalMilliseconds } } |
    Group-Object Name |
    Select-Object Name, @{ name = "AverageTime"; expression = { ($_.Group | Measure-Object Time -Average).Average } } |
    Sort-Object AverageTime |
    Format-Table Name, @{ label = "AverageTime(msec)"; expression = { $_.AverageTime -as "int" } } -AutoSize
}

#Import-Module ".\looptest.dll" -Cmdlet "Get-Twice"

# $src = @"
# using System;
# using System.Linq;

# public class LoopTest
# {
#     public static int[] Twice(object[] array)
#     {
#         return array.Select(x => 2 * (int)x).ToArray();
#     }
# }
# "@
# Add-Type -TypeDefinition $src -Language CSharp

filter TwiceFilter { 2 * $_.Where( { [IO.FileInfo] -eq $_.GetType() }).LastWriteTime.Second }
function TwiceFunction { process { 2 * $_.Where( { [IO.FileInfo] -eq $_.GetType() }).LastWriteTime.Second } }
function TwiceAdvance { param([Parameter(ValueFromPipeline)][IO.FileSystemInfo]$v) process { 2 * $v.Where( { [IO.FileInfo] -eq $v.GetType() }).LastWriteTime.Second } }

$foreachScripts = @(
    [pscustomobject]@{
        Name   = "ドットソース演算子(.)"
        Script = { $array | . { process { 2 * $_.Where( { [IO.FileInfo] -eq $_.GetType() }).LastWriteTime.Second } } }
    }
    [pscustomobject]@{
        Name   = "呼び出し演算子(&)"
        Script = { $array | & { process { 2 * $_.Where( { [IO.FileInfo] -eq $_.GetType() }).LastWriteTime.Second } } }
    }
    [pscustomobject]@{
        Name   = "filter"
        Script = { $array | TwiceFilter }
    }
    [pscustomobject]@{
        Name   = "関数"
        Script = { $array | TwiceFunction }
    }
    [pscustomobject]@{
        Name   = "高度な関数"
        Script = { $array | TwiceAdvance }
    }
    [pscustomobject]@{
        Name   = "ForEach-Object"
        Script = { $array | ForEach-Object { 2 * $_.Where( { [IO.FileInfo] -eq $_.GetType() }).LastWriteTime.Second } }
    }
    [pscustomobject]@{
        Name   = "ForEachメソッド"
        Script = { $array.ForEach( { 2 * $_.Where( { [IO.FileInfo] -eq $_.GetType() }).LastWriteTime.Second }) }
    }
    [pscustomobject]@{
        Name   = "foreach文"
        Script = { foreach ($i in $array) { 2 * $i.Where( { [IO.FileInfo] -eq $i.GetType() }).LastWriteTime.Second } }
    }
    [pscustomobject]@{
        Name   = "for文"
        Script = { for ($i = 0; $i -lt $array.Length; $i++) { 2 * $array[$i].Where( { [IO.FileInfo] -eq $array[$i].GetType() }).LastWriteTime.Second } }
    }
    [pscustomobject]@{
        Name   = "while文"
        Script = { $i = 0; while ($i -lt $array.Length) { 2 * $array[$i].Where( { [IO.FileInfo] -eq $array[$i].GetType() }).LastWriteTime.Second; $i++ } }
    }
    [pscustomobject]@{
        Name   = "switch文"
        Script = { switch ($array) { default { 2 * $_.Where( { [IO.FileInfo] -eq $_.GetType() }).LastWriteTime.Second } } }
    }
    [pscustomobject]@{
        Name   = "Select(LINQ)"
        Script = { [System.Linq.Enumerable]::Select($array, [Func[object, IO.FileSystemInfo]] { param($i) 2 * $i.Where( { [IO.FileInfo] -eq $i.GetType() }).LastWriteTime.Second }) }
    }
    # [pscustomobject]@{
    #     Name   = "C# (Add-Type)"
    #     Script = { [LoopTest]::Twice($array) }
    # }
    #[pscustomobject]@{
    #    Name = "コマンドレット(Binary Module)"
    #    Script = { $array | Get-Twice }
    #}
)

$files = Get-ChildItem -Recurse "$env:ProgramFiles"
$files.Count
$array = $files
$type = $files[0].GetType().BaseType.Name
$n = 50 # ループ1種類辺り計測回数

"*" * 60
"各種ループでサイズ$($array.Count)の${type}型配列の各要素に2をかけた値を取得するテスト"
"${n}回ずつ計測して平均タイムをミリ秒で取得"
"*" * 60

Test $foreachScripts $n