9.0 nuget version with 8.15.4 ES instance - not working Indices.Exists method

[kplazinski]

Hello, is new version of nuget should work with 8.15.4 ES instance?
It seems that there is some problem with calling Exists method on the index - I always got the error 400 (doesn't matter if index exists or not), so for example this code always show this error:

var settings = new ElasticsearchClientSettings(new Uri("http://localhost:9200"));
var client = new ElasticsearchClient(settings);
var output = client.Indices.Exists("anything");

[EDIT]
as a workaround I see that when sending this header it's working fine:

var nvc = new System.Collections.Specialized.NameValueCollection
{
   { "Accept", "application/vnd.elasticsearch+json;compatible-with=8" }
};
GlobalHeaders(nvc);

[flobernd]

Hi @kplazinski, the 9.x versions of the client are indeed not meant to be used with 8.x clusters.

The workaround should technically work (for now), but please note that we don't officially support this scenario.