Synchronize CSV Contact List to Active Directory Global Address List

Update-GAL.ps1

# NOTE: param() MUST BE FIRST STATEMENT in script file!!!
param([Parameter(Mandatory=$true)] $csvPath)

$ErrorActionPreference = "Stop"
Set-StrictMode -Version Latest
Import-Module ActiveDirectory

# Get the CSV file path from an input parameter ($csvPath)
$people = Import-CSV $csvPath
# CONVERT EMPTY STRING FIELDS TO $null
foreach ($person in $people) { 
    foreach ($property in $person.psobject.properties) { 
        if ($property.Value.Length -eq 0) { # zero length string
            $property.Value = $null; # convert to $null
}}}
# NOW WE CAN COMPARE NULL VALUES ...
foreach ($person in $people) {
    $adUser = $null # default value
    # Must specify ALL RELEVANT PROPERTIES otherwise they will NOT BE RETRIEVED with user objects
    try { $adUser = Get-AdUser $person.login -Properties otherTelephone,MobilePhone,OfficePhone,pager,Department,Manager }
    catch [Microsoft.ActiveDirectory.Management.ADIdentityNotFoundException] { } # keep null
    if ($adUser -ne $null) {
        #"Found AD User $($person.login)"
        # Lookup manager distinguished name in AD
        $mgrDN = $null # default value
        try { 
            if ($person.mgrLogin -ne $null) {
                $mgrDN = (Get-AdUser $person.mgrLogin).DistinguishedName
            }
        } catch [Microsoft.ActiveDirectory.Management.ADIdentityNotFoundException] { } # keep null

        $change = $false
        if (
            ($person.offsitePhone -eq $null -and $adUser.otherTelephone.Count -gt 0) -or # missing in ADP, present in AD
            ($person.offsitePhone -ne $null -and $adUser.otherTelephone.Count -gt 0 -and $person.offsitePhone -ne $adUser.otherTelephone[0]) -or # present in both, different values
            $person.cellPhone -ne $adUser.MobilePhone -or
            $person.officePhone -ne $adUser.OfficePhone -or
            $person.pager -ne $adUser.pager -or
            $person.dept -ne $adUser.Department -or
            $mgrDN -ne $adUser.Manager
        ) {
            # records are different, update AD-Object with data from ADP
            "=" * 48
            "Record before change \\\\\\\/////"
            $adUser | Select Name,SamAccountName,otherTelephone,MobilePhone,OfficePhone,pager,Department,Manager
            if ($person.offsitePhone -ne $null) { # we have an offsite phone
                if ($adUser.otherTelephone.Count -lt 1) { # need to expand list (currently empty)
                    $null = $adUser.otherTelephone.Add("")
                }
                $adUser.otherTelephone[0] = $person.offsitePhone
            } else { # we don't have an offsite phone
                $adUser.otherTelephone.Clear() # clear list in AD
            }
            $adUser.MobilePhone = $person.cellPhone
            $adUser.OfficePhone = $person.officePhone
            $adUser.pager = $person.pager
            $adUser.Department = $person.dept
            $adUser.Manager = $mgrDN
            "Record with updates \\\\\\\/////"
            $adUser | Select Name,SamAccountName,otherTelephone,MobilePhone,OfficePhone,pager,Department,Manager
            Set-ADUser -Instance $adUser #write the changes
        }
    } else {
        "MISSING AD USER $($person.login)"
    }
}

Example to synchronize contents of CSV file to Active Directory / Microsoft Exchange Global Address List (AD GAL). This is a typical load task from an ETL project (Extract, Transform, Load). PowerShell makes the task a little easier. Note that we're using pipeline output to show the object before and after modification - this can be saved to a log file for review if desired.