Styjun

I am building a script to pull the mac addresses of a computer, and convert them to GUIDs that are then queried to AD to find a match and retrieve the hostname associate with that guid.

Everything I've read about "Foreach" suggests that the code I am using "SHOULD" work.

$NIC = Get-WMIObject Win32_NetworkAdapterConfiguration | select MacAddress
$NICMacs = $NIC.MacAddress

Foreach ($NICMac in $NICMacs)
{

$MacString = $NICMacs -replace ":", ""
$MactoGUID = "00000000000000000000" + $MacString
$MactoGUID = $MactoGUID -replace " ", ''
$NBG = [GUID]$MactoGUID
$CompDetails = Get-ADComputer -Filter 'netbootGUID -like $NBG' -Properties netBootGUID -Server our.AD.server.ca -Credential $sessionKey

This should process each mac address found, stripping away the: characters and prepending 20 '0s' then convert to GUID format and query AD for a match.
Instead, it takes all the mac addresses found, concatenates them to one line and tries to process with all those numbers. Of course AD rejects it as an incorrect GUID.
If I use the same code with only 1 mac address, it is correctly formatted.

Some of your steps can be combined and thus save intermediate vars using

• Select-Object -ExpandProperty MacAddress


• 
  .PadLeft() method

As @RobV already pointed out in his comment usage of the wrong var caused the malfunction.

Foreach ($NICMac in (Get-WMIObject Win32_NetworkAdapterConfiguration |
 Where-Object MacAddress -ne '' |
 Select-Object -ExpandProperty MacAddress) ) 
 $NBG = [GUID]($NICMac -replace ':').PadLeft(32,'0')
 $CompDetails = Get-ADComputer -Filter 'netbootGUID -like $NBG' `
 -Properties netBootGUID -Server our.AD.server.ca -Credential $sessionKey

I don't consider usage of a line continuation character esoteric,

here it allows keeping the overview.

I agree that Natural Line Continuations in PowerShell are preferable.

A couple items here:

1. In your code, in line 7, you reference $NICMacs, but you should be referencing $NICMac since the foreach is running through the logic separately, not as a batch.


2. You could simplify at least the top two lines into a single line without a pipe.

$NICMacs = (Get-WMIObject Win32_NetworkAdapterConfiguration).MacAddress

Foreach ($NICMac in $NICMacs)
{

$MacString = $NICMac -replace ":", ""
$MactoGUID = "00000000000000000000" + $MacString
[GUID]$NBG = $MactoGUID -replace " ", ''
$CompDetails = Get-ADComputer -Filter 'netbootGUID -like $NBG' -Properties netBootGUID -Server our.AD.server.ca -Credential $sessionKey

Edit: in my suggested code, I think making $NBG should work with the [GUID] tag in front but I've never tried it