Why is my foreach variable not going to my output in PowerShell after each iteration?

Question

I have DHCP script that looks for matching hostnames in all the scopes on the DHCP servers

• I first get all the DHCP servers and import a .txt of hostnames

$list = Get-Content C:\script\HostNameList.txt #Defines content it pulls as list 
$DHServers = Get-DhcpServerInDC #gives variable name for loop

 # Gets all DHCP servers ands scopes 
    foreach ($Server in $DHServers){
        $scopes = Get-DHCPServerv4Scope -ComputerName $Server.dnsname #get all scopes
    }

• I loop through list of hostnames and scopes looking for a match. Somewhere in here is my issue

$Output = foreach ($hostname in $list) { #Calls each item in list a hostname and sends to output
    if (test-connection -count 1 -computername $hostname -quiet) #With 1 ping, check if hostname is online
    {   
        foreach ($scope in $scopes){ 
            if($scope | Get-DhcpServerV4Lease -ComputerName $server.dnsname | Where-Object HostName -like "$hostName*" ) #compares the hostname to lease to find which scope it is in
            { $scope.name } #return scope it found hostname in
        }
        [PSCustomObject]@{ #Rename varibles in data pull for output file
        Asset = $hostname
        Location = $scope.name #only want the name of the scope
        Status = "Online"
        }
    }   

    else #statement if hostname is not online
    { 
        Write-host "$hostname Is offline, only Last Location is known. $hostname was added to the output file." -BackgroundColor DarkRed
        [PSCustomObject]@{
        Asset = $hostname
        Location = $scope.name #only want the name of the scope, since the name = Location
        Status = "Offline"
        }
    }
}
$Output #show output in powershell
$Output | Export-Csv -Path C:\script\Asset_Result.csv -NoTypeInformation #outputs .csv

• This is what it is doing, the output repeats the last item on the list of DHCP scopes.

Asset    Location         Status
-----     --------         ------
A847    Public Internet      Online
A261    Public Internet      Offline
A201    Public Internet      Online

• This is what it should be doing

Asset    Location         Status
-----     --------         ------
A847        FLoor 1         Online
A261      West 1st FL       Offline
A201        Floor 3         Online

How can I get $scope.name in my if($scope | ... statement to go to my PSCustomObject after each iteration?

Answer 1

This:

foreach ($Server in $DHServers){
  $scopes = Get-DHCPServerv4Scope -ComputerName $Server.dnsname #get all scopes
}

is - in net effect - the equivalent of:

$scopes = Get-DHCPServerv4Scope -ComputerName $DHServers[-1].dnsname #get all scopes

That is, you keep reassigning to the same variable ($scopes) in the loop body, replacing the previous value, so that you end up with only the result from the last loop iteration, for the last server stored in $DHServers, i.e. $DHServers[-1].

---

The best solution is to rely on PowerShell's ability to use statements such as foreach as an expression whose output - even iterative output from a loop - is automatically collected in an [object[]] array (with two or more outputs) by PowerShell:

# Collect the output from *all* Get-DHCPServerv4Scope calls.
[array] $scopes = foreach ($Server in $DHServers) {
  Get-DHCPServerv4Scope -ComputerName $Server.dnsname #get all scopes
}

^{Note: The [array] type constraint (same as: [object[]]) is only necessary if there can situationally be just one output object and you want to ensure that the collected output is always an array.}