Sorry for the continued conversion trouble with this scenario. As you may have noticed in other forum threads, this Converter depends on the open source NRefactory engine to do its conversions between languages. In general, we try to support any conversion features natively supported by NRefactory. It seems that the conversion engine does not yet well handle these cross-language string concats.
We'll do some research and see if a newer version of NRefactory now solves the issue. In the meantime, we suggest that you share feedback on the engine's conversion accuracy with the NRecfactory development community.
Hope that helps. Thanks for highlighting this conversion scenario.