Using Invoke-Command to Get Application Pools on Remote Servers - arrays

Question

I'm attempting to use Invoke-Command to get a list of application pools on multiple remote servers. So far I have something like:
$servers = Get-Content -Path "C:\Path\to\servers.txt"
$array = New-Object -TypeName 'System.Collections.ArrayList'
foreach ($server in $servers) {
Invoke-Command -ComputerName $server -ScriptBlock {
Import-Module WebAdministration
$sites = Get-ChildItem IIS:\sites
foreach ($site in $sites) {
$array.Add($site.bindings)}}}
However I get the error:
You cannot call a method on a null-valued expression.
+ CategoryInfo : InvalidOperation: (Add:String) [], RuntimeException
+ FullyQualifiedErrorId : InvokeMethodOnNull
+ PSComputerName : computername
I've tried using regular arrays instead of ArrayLists and I get the following error:
Method invocation failed because [Microsoft.IIs.PowerShell.Framework.ConfigurationElement] doesn't contain a method named 'op_Addition'.
+ CategoryInfo : InvalidOperation: (op_Addition:String) [], RuntimeException
+ FullyQualifiedErrorId : MethodNotFound
+ PSComputerName : computername
Can anyone help point me in the right direction?

Answer 1

Your object $arrayis not known on your remote servers. So, one proposition is to send your array to the remote server, then add some values and return it :
$servers = Get-Content -Path "C:\Path\to\servers.txt"
$array = New-Object -TypeName 'System.Collections.ArrayList'
foreach ($server in $servers) {
$array = Invoke-Command -ComputerName $server -ScriptBlock {
param($array)
Import-Module WebAdministration
$sites = Get-ChildItem IIS:\sites
foreach ($site in $sites) {
[void]($array.Add($site.bindings))
}
$array
} -ArgumentList $array
}