Scroll example in ElasticSearch NEST API

Here's an example of using scroll with NEST and C#. Works with 5.x and 6.x

public IEnumerable<T> GetAllDocumentsInIndex<T>(string indexName, string scrollTimeout = "2m", int scrollSize = 1000) where T : class      {          ISearchResponse<T> initialResponse = this.ElasticClient.Search<T>              (scr => scr.Index(indexName)                   .From(0)                   .Take(scrollSize)                   .MatchAll()                   .Scroll(scrollTimeout));          List<T> results = new List<T>();          if (!initialResponse.IsValid || string.IsNullOrEmpty(initialResponse.ScrollId))              throw new Exception(initialResponse.ServerError.Error.Reason);          if (initialResponse.Documents.Any())              results.AddRange(initialResponse.Documents);          string scrollid = initialResponse.ScrollId;          bool isScrollSetHasData = true;          while (isScrollSetHasData)          {              ISearchResponse<T> loopingResponse = this.ElasticClient.Scroll<T>(scrollTimeout, scrollid);              if (loopingResponse.IsValid)              {                  results.AddRange(loopingResponse.Documents);                  scrollid = loopingResponse.ScrollId;              }              isScrollSetHasData = loopingResponse.Documents.Any();          }          this.ElasticClient.ClearScroll(new ClearScrollRequest(scrollid));          return results;      }

It's from: http://telegraphrepaircompany.com/elasticsearch-nest-scroll-api-c/

Internal implementation of NEST Reindex uses scroll to move documents from one index to another.

It should be good starting point.

Below you can find interesting for you code from github.

var page = 0;var searchResult = this.CurrentClient.Search<T>(    s => s        .Index(fromIndex)        .AllTypes()        .From(0)        .Size(size)        .Query(this._reindexDescriptor._QuerySelector ?? (q=>q.MatchAll()))        .SearchType(SearchType.Scan)        .Scroll(scroll)    );if (searchResult.Total <= 0)    throw new ReindexException(searchResult.ConnectionStatus, "index " + fromIndex + " has no documents!");IBulkResponse indexResult = null;do{    var result = searchResult;    searchResult = this.CurrentClient.Scroll<T>(s => s        .Scroll(scroll)        .ScrollId(result.ScrollId)    );    if (searchResult.Documents.HasAny())        indexResult = this.IndexSearchResults(searchResult, observer, toIndex, page);    page++;} while (searchResult.IsValid && indexResult != null && indexResult.IsValid && searchResult.Documents.HasAny());

Also you can take a look at integration test for Scroll

[Test]public void SearchTypeScan(){    var scanResults = this.Client.Search<ElasticsearchProject>(s => s        .From(0)        .Size(1)        .MatchAll()        .Fields(f => f.Name)        .SearchType(SearchType.Scan)        .Scroll("2s")    );    Assert.True(scanResults.IsValid);    Assert.False(scanResults.FieldSelections.Any());    Assert.IsNotNullOrEmpty(scanResults.ScrollId);    var results = this.Client.Scroll<ElasticsearchProject>(s=>s        .Scroll("4s")         .ScrollId(scanResults.ScrollId)    );    var hitCount = results.Hits.Count();    while (results.FieldSelections.Any())    {        Assert.True(results.IsValid);        Assert.True(results.FieldSelections.Any());        Assert.IsNotNullOrEmpty(results.ScrollId);        var localResults = results;        results = this.Client.Scroll<ElasticsearchProject>(s=>s            .Scroll("4s")            .ScrollId(localResults.ScrollId));        hitCount += results.Hits.Count();    }    Assert.AreEqual(scanResults.Total, hitCount);}

I took the liberty of rewriting the fine answer from Michael to async and a bit less verbose (v. 6.x Nest):

public async Task<IList<T>> RockAndScroll<T>(    string indexName,    string scrollTimeoutMinutes = "2m",    int scrollPageSize = 1000) where T : class{    var searchResponse = await this.ElasticClient.SearchAsync<T>(sd => sd        .Index(indexName)        .From(0)        .Take(scrollPageSize)        .MatchAll()        .Scroll(scrollTimeoutMinutes));    var results = new List<T>();    while (true)    {        if (!searchResponse.IsValid || string.IsNullOrEmpty(searchResponse.ScrollId))            throw new Exception($"Search error: {searchResponse.ServerError.Error.Reason}");        if (!searchResponse.Documents.Any())            break;        results.AddRange(searchResponse.Documents);        searchResponse = await ElasticClient.ScrollAsync<T>(scrollTimeoutMinutes, searchResponse.ScrollId);    }    await this.ElasticClient.ClearScrollAsync(new ClearScrollRequest(searchResponse.ScrollId));    return results;}