# Elasticsearch NEST FunctionScoreQuery

**URL:** <https://discuss.elastic.co/t/elasticsearch-nest-functionscorequery/308602>\
**Category:** Elasticsearch\
**Tags:** language-clients\
**Created:** [June 30, 2022, 3:35pm UTC](https://discuss.elastic.co/t/elasticsearch-nest-functionscorequery/308602 "2022-06-30T15:35:43Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Hristo\_Hristov](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/hristo_hristov/32/84268_2.png) [@Hristo\_Hristov](https://discuss.elastic.co/u/Hristo_Hristov)\
**Post date:** [June 30, 2022, 3:35pm UTC](https://discuss.elastic.co/t/elasticsearch-nest-functionscorequery/308602/1 "2022-06-30T15:35:43Z")

</div>

Hi,  
I am using Elasticsearch NEST (7.17.4) with ElasticSearch 8.2.3 to build search request.  
After added FunctionScoreQuery with Functions param i received exception "Can not write function score json for FunctionScoreFunction".

```auto
var funcScoreQry = new FunctionScoreQuery
                {
                    Query = boolQry,
                    Functions = GetFunctionScoreFunctions()
                };
                searchRequest.Query = funcScoreQry;

```

```auto
private IEnumerable<IScoreFunction> GetFunctionScoreFunctions()
        {
            var result = new List<IScoreFunction>();

            result.Add(new FunctionScoreFunction {
                Filter = new MatchQuery
                {
                    Field = "func",
                    Query = "1"
                },
                Weight = 2
            });

            return result;
        }

```

The Query (boolQry) is fine. If i remove Functions and just add other params (boost etc.) it's working.

The exception is thrown when i pass value to Functions property.

I coundn't find much on the problem so hope somebody could share experience using Score Functions.

Thanks

---

<div class="post-metadata">

**Author:** ![Hristo\_Hristov](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/hristo_hristov/32/84268_2.png) [@Hristo\_Hristov](https://discuss.elastic.co/u/Hristo_Hristov)\
**Post date:** [July 4, 2022, 7:02am UTC](https://discuss.elastic.co/t/elasticsearch-nest-functionscorequery/308602/2 "2022-07-04T07:02:49Z")

</div>

> [@Hristo\_Hristov](#):
>
> ```auto
> 
> ```

I changed FunctionScoreFunction to WeightFunction and it's working.

---

<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [August 1, 2022, 7:03am UTC](https://discuss.elastic.co/t/elasticsearch-nest-functionscorequery/308602/3 "2022-08-01T07:03:12Z")

</div>

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