Question

Given an SPListItem representing a folder, I need to find out whether it has the builtin folder content type, or a custom folder content type (with additional fields).

Here is what I do

    SPContentType folderType = aFolderItem.Web.AvailableContentTypes[SPBuiltInContentTypeId.Folder];
    SPContentType contentType = aFolderItem.ContentType;

    if ( contentType != folderType )
       ...

However, for default folders I still get a different content type than the built in type. They have IDs like 0x0120007C34D9760794FA43AB267F4E1A1BF460 . I m not sure where this particular GUID suffix comes from, I can t find it in any of the definition of my features folder.

My best guess is that instantiated folders always get a custom type. If that s the case, any suggestion on how I might be able to differentiate between builtin folders and custom folders?

Answer 1

If a content type is attached to a list, then it will not be attached directly but a copy of it will be created and attached. The original content type id is then annexed with a Guid and becomes the "new" content type s id.

If you kept to the guide lines for defining content type ids, then you custom folder content type id should look something like 0x0120 + 00 + <Guid>.

So if you check an item s content type whether it is a default or a custom folder, the id of a custom folder will look something like 0x0120 + 00 + <Guid> ==> Base folder content type id + a Guid for attaching it to a list.

In contrast to that the id of a custom folder will look something like 0x0120 + 00 + <Guid> + <Guid> ==> Base folder content type + a Guid for your custom content type + a Guid for attaching it to a list.

To make the comparison a little bit easier you should not compare the actual content type s id but have a look at the content type id s parent id. For a custom folder the parents id is 0x0120, for a custom folder it will be 0x0120 + 00 + <Guid>.

Answer 2

Assuming that aFolderItem is the Variable of type SPListItem below code should get what you want.

if(aFolderItem.ContentType.Id.IsChildOf(SPBuiltInContentTypeId.Folder))
          ...this is a Folder
else
          ...this is not a Folder

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