Configure build path with Capella Studio

Hi everyone,
While trying to implement a custom service ( mainly inspired by the basicMass VP ) for a Viewpoint, I raise an error while trying to use the eContents() method.
“The type org.eclipse.emf.common.util.EList cannot be resolved. It is indirectly referenced from required .class files”
Comparing to the basic VP, added some Required-Bundles to the Manifest.MF using the eclipse menu inteface, in order to have the same that in the basic VP.
However, the problem remains.
Has anyone had to cope with that issue once ?