public override bool Evaluate(FileMetadata fileMetadata)
        {
            var target = _source.ValueFrom(fileMetadata);
            var op     = target.GetType().GetMethod("op_Equality");

            if (op == null || op.ReturnType != typeof(bool))
            {
                return(false);
            }
            return((bool)op.Invoke(target, new[] { _comparand }) ^ _not);
        }