change editor and author of a document via powershell CSOM

Question

I am wanting to change the editor and author of a document in a document library in O365 using CSOM powershell. I have managed to change the dates like this :

$Upload = $List.RootFolder.Files.Add($FileCreationInfo)
$Context.Load($Upload)
$Context.ExecuteQuery()

$ListItem = $Upload.ListItemAllFields;

$Listitem["Modified"] = "2013-07-02T00:00:00"
$Listitem["Created"] = "2013-07-02T00:00:00"

$ListItem.Update()
$Context.Load($Upload)
$Context.ExecuteQuery()

but I am stuck with how to add people as $Listitem["Editor"] = "John Smith" doesn't work

Answer 1

Author and Editor fields are lookup fields. If you don't know the User ID you can get it by doing something like:

$user = $context.Web.EnsureUser($userEmail)
$context.Load($user)
$context.ExecuteQuery()

Then in your code you can set the lookup value. By providing a formatted string as follows:

$item["Editor"] = "{0};#{1}" -f $user.Id, $user.LoginName

Interestingly, it might seem that using a FieldUserValue is the appropriate way to do this:

$userValue = New-Object Microsoft.SharePoint.Client.FieldUserValue
$userValue.LookupId = $user.Id
$item["Editor"] = $userValue

But that fails (or it does for me).

UPDATE: I created a blog with full PowerShell source here: http://www.threewill.com/update-sharepoint-online-system-fields-via-csom/