While integrating various SharePoint features last week, I discovered some of the details around the dependency rules when trying to associate one feature to another.

In our solution, we have created a feature for specifying custom fields (i.e. columns) and content types. This feature is called the {Fabrikam Project1} Publication Content Types [company and project name replaced to protect the innocent ;-) ]. This makes it very easy to setup a new environment for our solution (e.g. DEV to TEST to PROD).

We have a different feature that builds out a custom version of the Document Center (a.k.a. the BDR or Business Document Repository), for example, to remove the default Documents doc lib, create a bunch of other doc libs instead, enable versioning on the doc libs, enable content types, set the default content type appropriately based on the particular doc lib, yadda, yadda, yadda.

This other feature is called {Fabrikam Project1} Publication Library, and naturally it has a dependency on the {Fabrikam Project1} Publication Content Types feature.

Originally, I had both features scoped to Site and setup a dependency from the Publication Library feature to the Publication Content Types feature:

<?xml version="1.0" encoding="utf-8"?>
<Feature xmlns="http://schemas.microsoft.com/sharepoint/"
  Id="49B204D0-7E35-4460-A691-A7D481C463B4"
  ...
  Scope="Site"
  ...
  ReceiverAssembly="Fabrikam.Project1.PublicationLibrary, Version=1.0.0.0, Culture=neutral, PublicKeyToken=8b7a42e9b9b5355f"
  ReceiverClass="Fabrikam.Project1.PublicationLibrary.Configuration.DefaultFeatureReceiver">
  <ActivationDependencies>
    <!-- Fabrikam.Project1.PublicationContentTypes -->
    <ActivationDependency FeatureId="9F5C14F1-CF58-47c7-BBBA-DA9A8637DEAB" />
  </ActivationDependencies>
  <ElementManifests>
  </ElementManifests>
</Feature>

I later realized that the Publication Library feature would be better scoped to WebApplication instead of Site (perhaps I'll blog about the reasons for this at another time), so I deactivated and uninstalled the feature, made a quick change to the Feature.xml file to change the scope, and then attempted to install and activate the updated feature. Unfortunately things did not go quite as smoothly as I had expected...

C:\NotBackedUp\Fabrikam\Project1\Main\PublicationLibrary\DeploymentFiles\Scripts>"Activate Feature.cmd"

Activating Fabrikam.Project1.PublicationLibrary on url - http://project1-local

Dependency feature 'Fabrikam.Project1.PublicationContentTypes' (id: 9f5c14f1-cf58-47c7-bbba-da9a8637deab) is not properly scoped for feature 'Fabrikam.Project1.PublicationLibrary' (id: 49b204d0-7e35-4460-a691-a7d481c463b4). Its scope 'Site' must be equal to or higher than 'WebApplication'.

Ouch...okay, no problem, I guess I'll just change the Publication Content Types feature to be scoped to WebApplication as well (instead of Site). Another quick deactivate, uninstall, XML file tweak, deploy, install, activate (I say "quick" only because of the scripts that we have to simplify the deployment) and...

C:\NotBackedUp\Fabrikam\Project1\Main\PublicationContentTypes\DeploymentFiles\Scripts>"Install Feature.cmd"

Installing Fabrikam.Project1.PublicationContentTypes

Elements of type 'Field' are not supported at the 'WebApplication' scope. This feature could not be installed.

Ugh...

Well, so if I want the Publication Library feature to be installed with Web Application scope, then I have no choice but to remove the dependency on the Publication Content Types feature. However, there really is a hard dependency on the other feature, so I really hate giving that up. After a couple of minutes, it came to me...

We already had a feature receiver for the Publication Library feature (as mentioned earlier to create and configure the Document Center). Why not just add a dependency check in there? Eureka!

namespace Fabrikam.Project1.PublicationLibrary.Configuration
{
    [CLSCompliant(false)]
    public sealed class FeatureConfigurator
    {
        readonly static Guid publicationContentTypesFeatureId =
            new Guid("9F5C14F1-CF58-47c7-BBBA-DA9A8637DEAB");
        
        private FeatureConfigurator() { } // all methods are static
        
        public static void Configure(
            SPWebApplication webApp)
        {
            if (webApp == null)
            {
                throw new ArgumentNullException("webApp");
            }
            
            Debug.WriteLine("Configuring Fabrikam.Project1.PublicationLibrary feature...");
            
            SPSite site = webApp.Sites["/"];
            
            // We cannot specify an explicit dependency on the PublicationContentTypes feature
            // because that feature must be scoped to 'Site' (since it contains Field elements).
            // Therefore we check this dependency via custom code when this feature is activated.
            SPFeature feature = site.Features[publicationContentTypesFeatureId];
            
            if (feature == null)
            {
                throw new InvalidOperationException(
                    "The Publication Content Types feature must be activated on the site"
                    + " in order to use the Publication Library feature.");
            }

            ...
        }
    }
}

Good enough for me!