Hashtableを使う場合

Add-Type @"
using System;
using System.Collections;
public class Helper {
public static void CallbackTest(Action<Hashtable> proc) {
var p = new Hashtable();
p["bState1"] = true;
p["bState2"] = true;
Console.WriteLine($"bState1:{p["bState1"]}, bState2:{p["bState2"]}");
proc(p);
Console.WriteLine($"bState1:{p["bState1"]}, bState2:{p["bState2"]}");
}
}
"@
[Helper]::CallbackTest({param($p);$p.bState1 | Out-Host;
$p.bState1 = $false;
$p.bState1 | Out-Host })