Activate-Once Hidden Farm Features

To create a dependent farm feature that is hidden and will activate only once, use a resource-hidden feature.  I explained Friday that hidden features automatically deactivate when the last feature dependent upon the hidden feature deactivates and that resource-hidden features do not.  So using a resource-hidden feature the feature does not deactivate.

The problem is that resource-hidden features do not automatically activate in the activation tree.  The solution for farm level features is to set the attribute ActivateOnDefault=”true” in the feature element API.  This will activate your farm level feature on deployment. Here is the feature.xml for the SPFeatureDefinition:

<?xml version="1.0" encoding="utf-8"?>
<Feature xmlns="http://schemas.microsoft.com/sharepoint/"
         Id="C595997F-F3DD-4677-82CF-02AF9FB73451"
         Title="$Resources:Resource_hidden_feature_DO_NOT_LOCALIZE"
         Description="$Resources:Resource_hidden_feature_DO_NOT_LOCALIZE"
         RequireResources="true"
         Hidden="false"
         Scope="Farm"
         ActivateOnDefault="true"
         ReceiverAssembly="My.Receiver.Assembly, Version=1.0.0.0, Culture=neutral, PublicKeyToken=8d63fadacc3f6a0e"
         ReceiverClass="My.Receiver.RunOnceFarmFeatureReceiver">
</Feature>

In this example the code in the SPFeatureReceiver is run only once at initial SPSolution.Deploy.  The feature is resource-hidden so users cannot see it and will not deactivate it from the Central Administration UI.  The feature also will not be deactivated by any features which depend on this feature.   The feature will only be deactivated prior to uninstall.