Issue
In VS2010, in a pattern toolkit project, an author may have one or more *.vstemplate files that contain their project and item templates. In those templates, at least two <WizardExtension> elements are defined, as such:
<WizardExtension>
<Assembly>NuPattern.Library, PublicKeyToken=ecdd31353928a4a5</Assembly>
<FullClassName>NuPattern.Library.Automation.InstantiationTemplateWizard</FullClassName>
</WizardExtension>
<WizardExtension>
<Assembly>NuPattern.Library, PublicKeyToken=ecdd31353928a4a5</Assembly>
<FullClassName>NuPattern.Library.Automation.ElementReplacementsWizard</FullClassName>
</WizardExtension>
The assembly names do not include the Version or Culture attributes, becuase this makes upgrading to new version of NuPattern much harder for the toolkit builder, and is currently a manual process.
In VS2012 however, the partial assembly names will not be loaded by VS. This is a change in behavior in VS2012, over what VS2010 did. Only fully qualified names will work, and so the assembly names need to include the Version and Culture attributes, viz:
<WizardExtension>
<Assembly>NuPattern.Library, Version=1.3.20.0, Culture=neutral, PublicKeyToken=ecdd31353928a4a5</Assembly>
<FullClassName>NuPattern.Library.Automation.InstantiationTemplateWizard</FullClassName>
</WizardExtension>
<WizardExtension>
<Assembly>NuPattern.Library, Version=1.3.20.0, Culture=neutral, PublicKeyToken=ecdd31353928a4a5</Assembly>
<FullClassName>NuPattern.Library.Automation.ElementReplacementsWizard</FullClassName>
</WizardExtension>
Resolution
The goal has always been to minimize manual changes in toolkit projects and their assets when new versions of NuPattern are released. For VSTemplates, this now seems unavoidable, where once the strategy was to avoid it.
At this time, there does not seem to be a hook into VS that can be intercepted to automatically interpret a partial name to a fully qualified name for VSTemplates.
Either a manual migraton process will be required when upgrading versions of NuPattern, or an automated process needs to be employed to upgrade existing pattern toolkit projects automatically when new versions of NuPattern are deployed.