Active Directory Script-Find if users exist

Question

Import-CSV "L:.\Users.txt" -header ("UserName") | % {
   $UserN = $_.UserName
   $ObjFilter = "(&(objectCategory=person)(objectCategory=User)(samaccountname=$UserN))"
   $User = Get-ADUser -Filter {sAMAccountName -eq $UserN}
 $objSearch = New-Object System.DirectoryServices.DirectorySearcher
 $objSearch.Filter = $ObjFilter 
 $objSearch.SearchRoot = "LDAP://ou=Remove this if you dont want only users in a OU returned,dc=Domain,dc=co,dc=uk"
 $AllObj = $objSearch.findOne()
 $user = [ADSI] $AllObj.path
 $ErrorActionPreference = "silentlycontinue"
 If ($User -eq $Null) {Write-host "Domain\$UserN does not exist in AD"}
 Else {Write-host "Domain\$UserN found in AD"}
-Can anybody help me step by step. I just started using powershell today. I am trying to use powershell to check if users exist in AD. I manage to create a script to check for one user at a time but, I really what a script to check multiple users at
the same time. This script is currently telling me everybody does not exist. Even if I put a user that does.

Answer 1

Thanks for the quick help & advice.
here are some example of names in the text file.
Flewellen,  Joel A
Golla  Wipperfurth,Linda
Grestner,   Allen
- I want to make sure the names in the text file do not exist in AD(Display name). Can I use your script for this? Again, I am a total noob.Currently reading about powershell.
 example does notwork:
Import-Module ActiveDirectory
Import-CSV "L:.\Users.txt" -header ("DisplayName") |
Foreach {
        if (Get-ADUser -Identity $_.DisplayName -ErrorAction SilentlyContinue) {Write-host "Domain\
$($_.DisplayName) found in AD"}       
        else {Write-host "Domain\$($_.DisplayName) does not exist in AD"}
I think i have to change the Get-ADUser -Identity $_.UserName