I'm in the process of migrating some of my discussion forum work from MOSS 2007 to SPS 2010, in preparation for two presentation. One is IW Community organised by Malaysia SharePoint usergroup, while the other is CTU 2009 II, organised by Singapore Community. When deploying the content type definitions using sandbox solution (I love this!!!), I get an error.
Error occurred in deployment step 'Activate Features': Key cannot be null.
Parameter name: key
Was looking at what did the product team added to the content type definition by looking at ctypes.xml, but found nothing. I copied their <FieldRef Name="Title" .../> to my content type, and deployment went successfully!!! I started to work with CAML during SharePoint 2003. At that time, xml tags are still using this syntax, <FieldRef Name="Name"></FieldRef>. The more modern way of doing this is <FieldRef Name="Name" />. I always thought they are the same, just less typing only. But since I don't have any more clues, I just tried changing the syntax, and the error go away...
So in SharePoint world, the two syntax means different thing. Is it the same in .Net world??