Search and Pagination in .Net

I am looking for an example of how to use search_after for pagination using the elastic.client in c#. I can see where the method is and that it takes a type of ICollection<FieldValue>? but I do not know how to get this from the previous search. Something like:

var lastHit = initialResponse.Hits.Last().Fields["sort"];

That I can pass into SearchAfter()