Q:

How to resolve "A duplicate contenet type name..." error for project with custom content types?

I have a project that I have been using to deploy a custom content type.  Recently i decided that I needed another content type that would inherit from the original one.  I created a new element file, added it the original feature and attempted to deploy.  At this point I was met with the following error:

Error occurred in deployment step 'Activate Features': A duplicate
  content type name "MNC Site Page" was found

Where MNC Site Page is my original content type.  How should I go about deploying an inheriting content type from the same project?
I tried removing the original content type from the feature but SharePoint then started complaining that the parent content type did not exist.....

A:

If your parent Content Type is already being used, it will not be removed when you do a Deactivate/Retract/Deploy/Activate cycle, as is done by Visual Studio. I think it's normal that SharePoint complains.
Try doing just an Update-SPSolution from the SP2010 Management Shell? Alternatively, package your 2nd content type in it's own feature and activate only that feature.

