how do i add dynamic highlight fields in nest for elasticsearch?

Question

i want to be able to dynamically add fields for highlighting in elasticsearch using nest. currently it looks like it's not a able to be iterated in any fashion.

i've tried iterating within the .OnFields function in order to produce a list of .OnField functions, but it says it's not iterable.

in this example, i want to dynamically add 'artist' and 'title' and add/remove others based on user input. is this possible?

s.Highlight(h => h
    .OnFields(f => f
        .OnField("artist")
        .OnField("title")
        .PreTags("<em>")
        .PostTags("</em>")
    ));

Answer 1

Highlight takes an array of Action<HighlightFieldDescriptor<T>> . You are only passing a single Action<HighlightFieldDescriptor<T>> and calling OnField multiple times on it, which keeps replacing the last value.

It should be this instead:

s.Highlight(h => h
    .OnFields(
        f => f.OnField("artist").PreTags("<em>").PostTags("</em>"),
        f => f.OnField("title").PreTags("<em>").PostTags("</em>")
    ));

From the code in your follow up post, here's a solution using LINQ:

s.Highlight(h => h
    .OnFields(
            SearchFields(searchDescriptor.SearchModifier).Select(x => new Action<HighlightFieldDescriptor>(f => f.OnField(x))).ToArray()
        ));

Answer 2

i realized i had confused a couple of types:

HighlightFieldDescriptor and HighlightDescriptor. sorry. here's my implementation (so i can mark as answered)

s.Highlight(h => h
            .OnFields(f => 
                GetFieldsHighligthDescriptor(searchDescriptor, f)
            )
        );

private void GetFieldsHighligthDescriptor(SearchQueryDescriptor searchDescriptor, HighlightFieldDescriptor<Product> f)
    {
        foreach (var b in SearchFields(searchDescriptor.SearchModifier))
        {
            f.OnField(b);
        }
    }

EDIT

actually, this isn't working because it's only return the last entry in my SearchFields array... back to the drawing board?