protected IList <IMoney> ConvertArgumentsToLocal( IBank bank, IMoney nonLocalAugend, IMoney nonLocalAddend) { var localAugend = bank?.ConvertToLocal(nonLocalAugend); var localAddend = bank?.ConvertToLocal(nonLocalAddend); if (localAugend == null || localAddend == null) { return(null); } return(new List <IMoney> { localAugend, localAddend }); }