Exception calling "Update" with "0" argument(s): "Invalid data has been used to update the list item. "

Question

I have an announcement list, where i need to populate it with some old data we have on emails, documents, etc. so i did the following:-

1.inside our Team site i added a new "Announcement list" . 2.then i wrote the following power-shell, to be able to add announcement items using our data, as follow:-

PS C:\Windows\system32> $web = get-spweb "http://servername/"
PS C:\Windows\system32> $list = $web.lists["News & Announcements"]
PS C:\Windows\system32> $newItem = $list.items.Add();
PS C:\Windows\system32> $newItem["Title"] = "123";
PS C:\Windows\system32> $newItem["Modified"] = "8/30/2015";
PS C:\Windows\system32> $newItem["Created"] = "6/30/2015";
PS C:\Windows\system32> $newItem["Body"] = "123456789 123456789";
PS C:\Windows\system32> $newItem["Editor"] = "test.user";
PS C:\Windows\system32> $newItem["Author"] = "test.user";
PS C:\Windows\system32> $newItem.Update();

but i got this error :-

Exception calling "Update" with "0" argument(s): "Invalid data has been used to update the list item. The field you are trying to update may be read only." At line:1 char:1 + $newItem.Update(); + ~~~~~~~~~~~~~~~~~ + CategoryInfo : NotSpecified: (:) [], MethodInvocationException + FullyQualifiedErrorId : SPException

so can anyone advice on this please?

Answer 1

Different points to note:

1. Use $list.AddItem() instead of $list.items.Add(). Much much better for performances.
2. You cannot set the Modified, Created, Author and Editor fields with a call to Update. You need to call the method UpdateOverwriteVersion instead.
3. In datetime fields (Modified, Created), you need to set actual DateTime values, e.g. New-Object System.DateTime(2015, 8, 30)
   EDIT: actually, this is true only in pure C# code... for PowerShell, you need to pass a string, see for instance http://sharepointcherie.blogspot.fr/2014/02/powershell-error-when-inserting-dates.html.
4. In users fields (Author, Editor), you need to set an SPUser object. You can get an SPUser object by using SPWeb.EnsureUser() method, e.g. $user = $web.EnsureUser("domain\LoginName")

PS C:\Windows\system32> $web = Get-SPWeb "http://servername/"  
PS C:\Windows\system32> $list = $web.Lists["News & Announcements"]  
PS C:\Windows\system32> $newItem = $List.AddItem()  
PS C:\Windows\system32> $newItem["Title"] = "123"  
PS C:\Windows\system32> $newItem["Body"] = "123456789 123456789"  
PS C:\Windows\system32> $newItem["Modified"] = "8/30/2015"  
PS C:\Windows\system32> $newItem["Created"] = "6/30/2015"  
PS C:\Windows\system32> $user = $web.EnsureUser("domain\test.user")  
PS C:\Windows\system32> $newItem["Editor"] = $user  
PS C:\Windows\system32> $newItem["Author"] = $user  
PS C:\Windows\system32> $newItem.UpdateOverwriteVersion()