Unable to call script block from Powershell script

Question

I am trying to execute a script when the user locks the computer. This is how my script looks like:

$OnLock = 
{
    Write-Host  -ForeGround Green "System Locked"
}


$sysevent = [microsoft.win32.systemevents]

Register-ObjectEvent -InputObject $sysevent -EventName "SessionSwitch" -Action {$OnLock} -SourceIdentifier "ExecuteOnLock"

The problem is that it does not print anything on the console window but if i write the code in the Action switch, it works fine.

Register-ObjectEvent -InputObject $sysevent -EventName "SessionSwitch" -SourceIdentifier "ExecuteOnLock" -Action {Write-Host  -ForeGround Green "System Locked"}

Is there something i am missing while calling $OnLock script block?

Remove the braces around $OnLock when you are calling it from the -Action parameter. — Benjamin Hubbard
– Benjamin Hubbard, Commented Oct 22, 2013 at 16:17

Benjamin Hubbard · Accepted Answer · 2013-10-22 18:37:02Z

2

Remove the braces around $OnLock when you are calling it from the -Action parameter.

answered Oct 22, 2013 at 18:37

Benjamin Hubbard

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Comments

mjolinor · Accepted Answer · 2013-10-22 16:16:28Z

1

Event actions run in a separate runspace that can't access local variables. Try making it a function in the Global scope.

Function Global:OnLock { 
Write-Host  -ForeGround Green "System Locked" }

$sysevent = [microsoft.win32.systemevents]

Register-ObjectEvent -InputObject $sysevent -EventName "SessionSwitch" -Action {OnLock} -SourceIdentifier "ExecuteOnLock"

answered Oct 22, 2013 at 16:16

mjolinor

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Comments

Andrei Odegov · Accepted Answer · 2017-05-26 20:23:23Z

I've discovered today a funny way to call local functions of a script from a scriptblock passed in the Action parameter of the Register-ObjectEvent cmdlet by using the MessageData parameter the previously mentioned cmdlet without attributing these functions to global scope. Look at the next code snippet:

&{  
  function sesbeg{
    'Lots of usfull actions in the "sesbeg" function'
  }
  function rqincs{
    'Lots of usfull actions in the "rqincs" function'
  }
  function sesfin{
    'Lots of usfull actions in the "sesfin" function'
  }
  function outincs{
    'Lots of usfull actions in the "outincs" function'
  }
  function shincs{
    sesbeg
    $my.incs=rqincs
    sesfin
    if($my.incs){$my.incs;outincs;$refr=$my.refr*1000}
    else{write-host 'The data was not received';$refr=1000}
    $my.tim.Interval=$refr
  }
  function tmbeg{
    $my.tim=New-Object System.Timers.Timer ($my.refr*1000)
    $my.tim.AutoReset=$True
    $my.subs=Register-ObjectEvent $my.tim Elapsed `
               -Action {$Event.MessageData|%{$my=$_.my;&$_.fn}|Out-Host} `
               -MessageData @{my=$my;fn=$function:shincs}
    $my.tim.Start()
  }
  $my=@{refr=5}
  tmbeg
  shincs
}

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