Unrelated column appears in Content type version history

Question

We have a site content type that inherits from Document and has 2 additional columns added to it. This Content types is used in a library along with 5 other content types. When we look at Version history there is only one version and it shows the 2 columns with data plus a column from another content type that is in that library.

The real issue is that when viewing the RSS for this library, the documents mentioned above show this 'rogue' column.

Is there a way to determine and remove the association of this column?

Answer 1

If you go into the list settings, click on the associated content type, then 'rogue' column, if you're lucky then you will have a "Remove" button. Failing that, the crack open PowerShell

$web = Get-SPWeb http://myWebUrl
$list = $web.Lists| ?{$_.Title -eq "MyListTitle"}
$ct = $lists.ContentTypes | ?{$_.Name -eq "Content Type Name} 
$field = $ct.Fields | ?{$_.Title -eq "Field Title"}
$ct.FieldLinks.Delete($field.Title)
$ct.Update()

Answer 2

I can think of a couple of potential scenarios causing this behaviour:

Firstly when you add a Site Content type to a list/library it basically creates a copy of that site content type in the list and it becomes a List Content type, new columns can be added to this list content type completely independently of the Site Content type, so its possible that this rogue column has been added directly to the List Content Type and may have a default value set? You can check this by looking at the content type from the Library Settings page.

Secondly the Content Type that is currently associated to a particular item doesn't necessarily prevent a value being set on a column that is not part of that content type. Every column added to a list is technically available to any item in the list. The SharePoint UI just makes it difficult to alter values in these other columns not associated with the current content type, but not impossible. Perhaps the rogue column is a calculated column, which depending on the calculation involved may always get a value? If this is the case you could refine the calculation, or remove the column from the list.