If you try to work with contextual tabs, you might want to use server side in order to make these tabs visible.
Please see a link here to a good article about this by Chris O'brien:
But, if you just create a new SharePoint solution these methods will not be available to you:
The reason is, that these 2 new commands are infact a part of Microsoft.Web.CommandUI DLL, which is available outside of the SharePoint DLL, hence when you only have a reference to SharePoint DLL's you will see the SPRibbon object but some functionality inherited from it's base type will be hidden.
So - add a reference to Microsoft.Web.CommandUI and you'll be good to go!