Highlighting all attachment fields

HighlightExtensions.cs

public static class HighlightExtensions
{
    public static IQueriedSearch<TSource, TExistingQuery> WithAttachmentHighlight<TSource, TExistingQuery>(
        this IQueriedSearch<TSource, TExistingQuery> search, Action<FieldHighlightRequest> highlightAction = null)
        where TExistingQuery : QueryStringQuery
    {
        return new Search<TSource, TExistingQuery>(search, context =>
        {
            var fieldName = "*$$attachment";
            var request = new FieldHighlightRequest(fieldName);
            if (highlightAction.IsNotNull())
            {
                highlightAction(request);
            }
            context.RequestBody.Highlight.Fields.Add(request);
        });
    }
}

Query.cs

result = client.Search<MyType>()
            .For("banana")
            .WithAttachmentHighlight()
            .GetResult();
            
result.Hits.First().Highlights.First().Highlights.First();