Deploying content types as a feature

This is the third article in my series of how to create common SharePoint site artifacts as features. Last time we looked at creating site columns as a feature.

Site columns are typically used in lists and/or content types. The concepts are fairly simple since a content type is also effectively a list with a series of columns (for those who have worked with CMS2002 the equivalent entity was a template definition). The columns give the data entered into content areas on a page somewhere to be stored. However, content types in SharePoint are also a valuable unit of granularity, since workflow, document lifecycle policy and several other key pieces of functionality can be configured at this level.

Any page layout you create as a template for pages on your site must be associated with a content type. Generally each column in the content type will be matched to a field control on the page layout, allowing the author to enter content to be stored in each column.

Fortunately creating content types as features is fairly simple - CAML only, no need for a feature receiver (code). Alas VSeWSS can't help us much here but don't forget to use the CAML schema intellisense in VS by ensuring the XML file we're about to write is linked to the schema at C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\XML\wss.xsd.

Initially, the part that can seem complex is the ID structure for a content type. Having been happily using GuidGen in Visual Studio every time we need an ID for something in a feature (though never trusting the first one ;-)), it comes as a surprise to have to read documentation just about IDs. As explained in Content Type IDs, the structure reflects the ancestry/parentage of a content type, meaning the parent content types can be determined very efficiently since simple string/byte matching can be used thus reducing database lookups.

The basics are:

• find the ID of the content type you are deriving from. This can be done by either examining the content type in the SharePoint UI (Site Settings > Manage Content Types) and copying the ID from the URL querystring. Alternatively, search the feature files which the MS developers used to deploy the out-of-the-box content types. The former is probably simpler but the latter gives more scope for learning.
• Add '00' and then a GUID you have generated (i.e. with GuidGen) to the end (suffix). You now have a valid content type ID. Note that you'll get a meaningful exception on feature activation if it's not.
• For any child content types, to generate their IDs you can now add a simple ID such as '01' or '02' to the ID generated in the previous step. It's not necessary to suffix the ID with '00' and another GUID now since your unique ID is in the string. This means any ID's you generate will be different from anyone else's, so you can use the simple option and use a 2 digit number rather than another GUID. This means your content type IDs shouldn't grow too long.

The rest is fairly simple. Just add a FieldRef element for each site column the content type uses, specifying it's ID and name. Note that the approach we used to create our site columns meant that we got to specify the ID for them in CAML. We just need to dig out the IDs we specified there. So in both features, the IDs are in easily edited XML rather than being in any compiled code or similar so they are fairly loosely-coupled. Of course in many cases you'd choose to have both artifacts in the same feature, and in the future I'll post about factoring with relation to features.

You should end up with something like for each content type you are deploying:-

<!-- this content type is derived from the 'Page' content type from the 'Publishing' feature -->
<ContentType ID="0x010100C568DB52D9D0A14D9B2FDCC96666E9F2007948130EC3DB064584E219954237AF3900CF38CCD7FC6E8247AA124F3EE5796C20"
   Name="COBArticle"
   Group="COB demo content types"
   Description="Base content type for articles."
   Version="0">
   <FieldRefs>
      <FieldRef ID="{ae8e6ab8-b151-4fa4-8694-3cd24ad3b1bc}" Name="Locations" />
      <FieldRef ID="{A4983A93-4B14-4a61-AE08-09108A718628}" Name="Sectors" />
      <FieldRef ID="{6F26090A-C2AE-44d7-8F70-EE1663FE29F1}" Name="Disciplines" />
      <FieldRef ID="{71316CEA-40A0-49f3-8659-F0CEFDBDBD4F}" Name="Article Date" />
   </FieldRefs>
</ContentType>

Note that it's not necessary to repeat the fields declared in parent content types, though I notice some of the Microsoft features do this.

So now you have your content types deployed, they can now be used in document libraries/lists or associated with any page layouts you have. So next time is deploying master pages/page layouts/CSS etc. as a feature, including having the layouts automatically bound to the content types.