internal override Expression VisitUnary(UnaryExpression u) { switch (u.NodeType) { case ExpressionType.Not: { NativeQuery.not(_coreQueryHandle); this.Visit(u.Operand); // recurse into richer expression, expect to VisitCombination } break; default: throw new NotSupportedException($"The unary operator '{u.NodeType}' is not supported"); } return(u); }