Hidden Content Types and Hidden Site Columns on MOSS 2007 and SharePoint 2010

You may know that several out-of-the-box Content Types belong to the group _Hidden.

This means that when you first start using the site, you cannot create child Content Types based on these types. Also, if you want to aggregate Blog Posts with a Content Query Web Part, for instance, you will need to expose the content type to the web part’s drop down configuration menus. This table lists the OOB Content Types that belong to the _Hidden group.

Name

Ctype

Administrative Task

0x010802

Comment

0x0111

DomainGroup

0x010C

Event

0x0102

Office Data Connection File

0x010100629D00608F814dd6AC8A86903AEE72AA

Person

0x010A

Post

0x0110

RootOfList

0x012001

SharePointGroup

0x010B

Universal Data Connection File

0x010100B4CBD48E029A4ad8B62CB0E41868F2B0

User Workflow Document

0x010107

Wiki Page

0x010108

Workflow History

0x0109

Workflow Task

0x010801

I listed the hidden ctype above because you can get to the settings quickly by using this path: http://<server_name>/_layouts/ManageContentType.aspx?ctype=<ctype>

Then click “Name, description, and group” to change the group. Since _Hidden does not appear in the dropdown, this is a one-way change without some sort of hack. I suggest moving these to a new group that you can monitor–you really don’t want someone to change the base Content Types, just creating their own child types. The same thing can happen to Site Columns. Next time you need an OOB Site Column for another Content Type or a Calculated Column and can’t find it, check to see if it’s actually in a _Hidden group. For example, if you create a child of Event, the field labeled Start Time is actually “StartDate” which you can use in a formula but End Time (internal name “EndDate”) is hidden.

After changing this group to a visible one, you can use End Time in calculations like =[End Time]-[Start Date].