How to stop a shutdown and do something with Powershell on Windows 10

Question

I would like to create a script that detect and delay a shutdown on Windows 10 PC's and show a Message if a USB-Stick is plugged in at the moment of the shutdown.

My problem is that my script is not stop the shutdown. Im pretty new to Powershell. Sry for my english.

This is what i got:

[System.Reflection.Assembly]::Load("System.Management, Version=2.0.0.0,
Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")

$Man = New-Object System.Management.ManagementClass("Win32_USBHub")
[System.Management.ManagementObjectCollection]$Devs = $Man.GetInstances()

$global:shuttingDown = $false
$sysevent = [microsoft.win32.systemevents]
Register-ObjectEvent -InputObject $sysevent -EventName "SessionEnding" -Action {$global:shuttingDown = $true; Write-Host "  SessionEnding"} 
Register-ObjectEvent -InputObject $sysevent -EventName "SessionEnded"  -Action {$global:shuttingDown = $true; Write-Host "  SessionEnded"} 

do {
    Start-Sleep -Seconds 1
        if ($global:shuttingDown) {
            & "$env:SystemRoot\System32\Shutdown.exe" -a ;

            $Devs | ForEach-Object {
            if($_.GetPropertyValue("Name").ToString() -eq "USB-Massenspeichergerät"){

                Add-Type -AssemblyName PresentationCore,PresentationFramework
                $ButtonType = [System.Windows.MessageBoxButton]::Ok
                $MessageboxTitle = “USB-Stick gefunden”
                $Messageboxbody = “Es wurde ein USB-Stick gefunden. Nicht vergessen mitzunehmen ;)”
                $MessageIcon = [System.Windows.MessageBoxImage]::Warning
                [System.Windows.MessageBox]::Show($Messageboxbody,$MessageboxTitle,$ButtonType,$messageicon)

                Write-Output ""
                Write-Output $_.GetPropertyValue("Name").ToString()
                Write-Output ""
            }
            $Devs.Dispose()
            $Man.Dispose()
        }
    }
    Write-Host "  Waiting for Shutdown"
} while ($true)

thx for your help

Answer 1

so basically, if $global:shuttingDown holds value then use a Break

do {
    Start-Sleep -Seconds 1
    if ($global:shuttingDown) {break}
    Write-Host " Waiting for Shutdown"
} while ($true)