There are particular site columns in SharePoint, which once added to a site content type or list cannot be removed again using the browser UI. An example of one of these columns in SharePoint Server 2010 is “Aliases”. If I add it to a content type and then click on the column name to remove it, you can see that the Remove button is not available.
This can cause much frustration and may even prompt you to completely delete the content type and start again – something that is usually impossible to do on a live environment.
Fortunately, we have PowerShell available to us for solving such problems. The script below will attach to the site containing your content type (also works for content type hubs), the content type itself, and then the link to the column within the content type. It then only takes a couple of lines to remove the column and update the content type.
The example below will remove the “Aliases” site column from the “Sales Document” site content type in http://portal:
#Attach to the web and content type
$web = Get-SPWeb http://portal
$ct = $web.ContentTypes["Sales Document"]#Get link to the columnn from the web
$spFieldLink = New-Object Microsoft.SharePoint.SPFieldLink ($web.Fields["Aliases"])#Remove the column from the content type and update
$ct.FieldLinks.Delete($spFieldLink.Id)
$ct.Update()#Dispose of the web object
$web.Dispose()
Phew!
Note that any columns of this type deleted from a parent content type will not automatically disappear in the child content types below it. The easiest way to get around this is to use the same script above to remove the site column from child content types, too.
Unfortunately, you may also find that if the content types containing this site column were attached to lists, then the lists themselves will also have the column added to them – even after removing the column from all associated content types. If this is the case, you will not be able to remove the column in the list using the browser UI as the Remove button will be missing on the column administration page here also.
To resolve this, you can either decide to remove the column using PowerShell one list at a time, or if there is a way of defining a batch of lists, use a script to modify multiple lists in one go. The script below provides you with an example of how to walk through each document library of a specified name on each site of the site collection and delete the offending column. If you do decide to run a script like this, please ensure you have fully tested it in a development environment beforehand due to the potential damage that it could inflict:
#Delete column on a specified list in all sites of a site collection
$site = Get-SPSite http://portal
$site | Get-SPWeb -Limit all | ForEach-Object {
#Specify list which contains the column
$list = $_.Lists["Pages"]
#Specify column to be deleted
$field = $list.Fields["Aliases"]
#Allow column to be deleted
$field.AllowDeletion = $true
#Delete the column
$field.Delete()
#Update the list
$list.Update()
}
$site.Dispose()
