Powershell - verify object exists in AD - powershell

Question

i have a text file containing arround 100 servers, how can i push these into a script and test if they exist within AD? I have a simple script below:
$serverlist = get-content ServerList.txt
foreach ($server in $serverlist) {
if (Get-ADComputer $serverlist ) {
Write-Host "#########################"
Write-Host "Computer object exists"
Write-Host "#########################"
}
else {
Write-Host "#########################"
Write-Host "Computer object NOT FOUND"
Write-Host "#########################"
}
}
the above does not work returning a error:
Get-ADComputer : Cannot convert 'System.Object[]' to the type 'Microsoft.ActiveDirectory.Management.ADComputer' required by parameter 'Identity'. Specified method is not supported.
Can someone please explain does the get-adcomputer only allow a single object? Also if i remove the txt file and add a server shown below:
if (Get-ADComputer "server name" )
The above provides only results if the server exists within AD, if the server does not the error is shown below:
Get-ADComputer : Cannot find an object with identity: 'iuiub' under: 'DC=####,DC=#####,DC=#####'
Thank you for any insight / help!
Phil

Answer 1

Create an array - #(). If the array has 1 or more objects in it - which is $true - then you know the computer exists. If the array has 0 objects in it - which is $false- then you know the computer doesn't exist. I know some people don't like the ErrorAction to be set to SilentlyContinue but you're "Outputting an Error" if an error does occur.
$serverlist = get-content ServerList.txt
foreach ($server in $serverlist) {
if (#(Get-ADComputer $server -ErrorAction SilentlyContinue).Count) {
Write-Host "#########################"
Write-Host "Computer object exists"
Write-Host "#########################"
}
else {
Write-Host "#########################"
Write-Host "Computer object NOT FOUND"
Write-Host "#########################"
}
}
Another thing you could try are try catch blocks. Sorta like this:
$serverlist = get-content ServerList.txt
foreach ($server in $serverlist) {
try{
Get-ADComputer $server -ErrorAction Stop
Write-Host "#########################"
Write-Host "Computer object exists"
Write-Host "#########################"
}
catch{
Write-Host "#########################"
Write-Host "Computer object NOT FOUND"
Write-Host "#########################"
}
}

Answer 2

Line 3, change $serverlist to $server
With regards to handling a not found result. I'd try flipping the logic :
$serverlist = get-content ServerList.txt
foreach ($server in $serverlist) {
$tempVar = Get-ADComputer $server
if ($tempVar -like "Get-ADComputer : Cannot find an object with identity" ) {
Write-Host "#########################"
Write-Host "Computer object NOT FOUND"
Write-Host "#########################"
}
else{
Write-Host "#########################"
Write-Host "Computer object exists"
Write-Host "#########################"
}
}

Answer 3

In order to get a more helpful output, I'd go with the following... You'll just have a list of green and red lines indicating which server was found and which one wasn't.
$serverlist = get-content ServerList.txt
foreach ($server in $serverlist) {
try {
Get-ADComputer $server -ErrorAction Stop | Out-Null
Write-Host "$($server) exists" -ForegroundColor DarkGreen
}
catch {
Write-Host "$($server) NOT FOUND" -ForegroundColor DarkRed
}
}