Unregisgter an eventObject

Hi:

I wonder what’s the common practice for unregistering a registered object in a shell script? My original thought is to wait for user’s prompt in console to terminate, and my code goes like this:

$watcher = New-Object System.IO.FileSystemWatcher
$watcher.IncludeSubdirectories = $false

$targetPath = 'C:\Users\Dell\Pictures\Screenshots'
$watcher.Path = $targetPath
$watcher.EnableRaisingEvents = $true
$action =
{
    $path = $event.SourceEventArgs.FullPath
    $changetype = $event.SourceEventArgs.ChangeType
    #Write-Host "$path was $changetype at $(get-date)"
}
Register-ObjectEvent $watcher "Created" -Action $action
while($true){
    $sentinal = read-host "Type no to quit"
    if ($sentinal -eq "no"){
        get-eventsubscriber -force | unregister-event -force
        break
    }
}

However, the script works different from my expectation. The action of registered events ( write path was $changetype at $(get-date) to console) was not triggered off until the whole script terminates. I wonder is there a way to resolve this or what’s the common practice for adding an unregister command.

Thanks in advance.