Elasticsearch NEST DisMax MoreLikeThis query forms empty json string

Question

I'd like to use moreLikeThis query on Elasticsearch using NEST library and give different boost values for each match.

var moreLikeThis = _elastic.Search<Report>(s => s
    .From(0)
    .Size(10)
    .Query(q => q
        .Filtered(f => f
            .Query(fq => fq
                .Dismax(dmx => dmx
                    .TieBreaker(0.7)
                    .Queries(qr => qr
                        .MoreLikeThis(mlt => mlt
                            .OnFields(of => of.Title.Suffix("stemmed"))
                            .MinTermFrequency(1)
                            .MaxQueryTerms(12)
                            .Boost(20)
                            .Documents(docs => docs
                                .Document()          // This is the part where I'm stuck
                            )
                        ), qr => qr
                        .MoreLikeThis(mlt => mlt
                            .OnFields(of => of.Title.Suffix("synonym"))
                            .MinTermFrequency(1)
                            .MaxQueryTerms(12)
                            .Boost(10)
                        )
                    )
                )
            )
        )
    )
);

This the query I'm stuck at. I can write this easily in raw JSON format, but that's not what I'm aiming for. I'm quite new in both C# and NEST and do not know how to pass documentId there.

That's my class, if it helps at all :

[ElasticType(IdProperty = "_id", Name = "reports")]
public class Report
{
    [ElasticProperty(Name = "_id", Type = FieldType.String)]
    public string _id { get; set; }

    [ElasticProperty(Name = "Title", Type = FieldType.String)]
    public string Title { get; set; }
}

And that's the query I'm using as JSON and it works just fine.

{
  "from": 0,
  "size": 10,
  "fields": ["Title"],
  "query": {
    "filtered": {
      "query": {
        "dis_max": {
          "tie_breaker": 0.7,
          "queries": [
            {
              "more_like_this": {
                "fields": ["Title.stemmed"],
                "docs": [
                  {
                    "_index": "test",
                    "_type": "reports",
                    "_id": "68753"
                  }
                ],
                "min_term_freq": 1,
                "max_query_terms": 12
              }
            }, {
              "more_like_this": {
                "fields": ["Title.synonym"],
                "docs": [
                  {
                    "_index": "test",
                    "_type": "reports",
                    "_id": "68753"
                  }
                ],
                "min_term_freq": 1,
                "max_query_terms": 12
              }
            }
          ]
        }
      }
    }
  }
}

Documentation in NEST doesn't explain or give a basic idea how this is done.

Thank you.

Answer 1

As stated in comments this was a bug and will be fixed together with 1.5.2 NEST release.