<#
  This script will find duplicate employeeID values and export them
  to a CSV file.

  Syntax examples:
    To process all users:
      UpdatingEmployeeID.ps1

    To process all users from a particular OU structure:
      UpdatingEmployeeID.ps1 -SearchBase "OU=Users,OU=Corp,DC=mydemosthatrock,DC=com" -ReferenceFile "c:\MyOutput.csv"

    You must use quotes around the SearchBase parameter otherwise the
    comma will be replaced with a space. This is because the comma is a
    special symbol in PowerShell.

  Release 1.0
  Written by [email protected] 3rd April 2014

#>

#-------------------------------------------------------------
param([String]$SearchBase, [String]$ReferenceFile)

# Get the script path
$ScriptPath = { Split-Path $MyInvocation.ScriptName }

if ([String]::IsNullOrEmpty($ReferenceFile)) {
    $ReferenceFile = $(&$ScriptPath) + "\DuplicateEmployeeIDs.csv";
}

$UsedefaultNamingContext = $False
if ([String]::IsNullOrEmpty($SearchBase)) {
    $UsedefaultNamingContext = $True
}

#-------------------------------------------------------------
# Import the Active Directory Module
Import-Module ActiveDirectory -WarningAction SilentlyContinue
if ($Error.Count -eq 0) {
    #Write-Host "Successfully loaded Active Directory Powershell's module" -ForeGroundColor Green
}
else {
    Write-Host "Error while loading Active Directory Powershell's module : $Error" -ForeGroundColor Red
    exit
}

#-------------------------------------------------------------
$defaultNamingContext = (get-adrootdse).defaultnamingcontext
$DistinguishedName = (Get-ADDomain).DistinguishedName
$DomainName = (Get-ADDomain).NetBIOSName
$DNSRoot = (Get-ADDomain).DNSRoot

if ($UsedefaultNamingContext -eq $True) {
    $SearchBase = $defaultNamingContext
}
else {
    $TestSearchBase = Get-ADobject "$SearchBase"
    if ($Null -eq $TestSearchBase) {
        $SearchBase = $defaultNamingContext
    }
}

#-------------------------------------------------------------

function Get-LastLoggedOnDate ([string] $Date) {
    if ($Date -eq $NULL -OR $Date -eq "") {
        $Date = "Never logged on before"
    }
    $Date
}

$LastLoggedOnDate = @{Name = 'LastLoggedOnDate'; Expression = { Get-LastLoggedOnDate $_.LastLogonDate } }

$EmployeeID = @{Name = 'EmployeeID'; Expression = { $_.EmployeeID.Trim() } }

$TotalProcessed = 0
$filter = "(employeeID=*)"
Write-Host -ForegroundColor Green "Finding all users with an employeeID attribute and exporting the duplicates to '$ReferenceFile'`n"
Get-ADUser -LDAPFilter $filter -SearchBase $SearchBase -Properties * | Select-Object $EmployeeID, SamAccountName, Name, Enabled, $LastLoggedOnDate, whenCreated | Group-Object EmployeeID | Where-Object { $_.Count -gt 1 } | Select-Object -Expand Group | Export-Csv -notype "$ReferenceFile"

# Remove the quotes
(Get-Content "$ReferenceFile") | ForEach-Object { $_ -replace '"', "" } | Out-File "$ReferenceFile" -Force -Encoding ascii