Working with Fields in NEST 5.0.1

Fields-with-NEST-5.0.1.cs

void Main()
{
    var pool = new SingleNodeConnectionPool(new Uri("http://localhost:9200"));
    var connectionSettings = new ConnectionSettings(pool);
    
    var client = new ElasticClient(connectionSettings);

/** 
  All the following produce the query json
  
  {
    "query": {
      "query_string": {
        "query": "search for this in post title, body, comments and tags",
        "fields": [
          "title",
          "body",
          "comments",
          "tags"
        ]
      }
    }
  }

*/


    // 1. use expressions for fields
    var fields = new Field[]
    {
        Infer.Field<Post>(f => f.Title),
        Infer.Field<Post>(f => f.Body),
        Infer.Field<Post>(f => f.Comments),
        Infer.Field<Post>(f => f.Tags)
    };

    var searchResponse = client.Search<Post>(m => m
        .Query(q => q
            .QueryString(qs => qs
                .Fields(f => f
                    .Fields(fields)
                )
                .Query("search for this in post title, body, comments and tags")
            )
        )
    );

    // 2. Use strings for fields
    fields = new Field[]
    {
        "title",
        "body",
        "comments",
        "tags"
    };

    searchResponse = client.Search<Post>(m => m
        .Query(q => q
            .QueryString(qs => qs
                .Fields(f => f
                    .Fields(fields)
                )
                .Query("search for this in post title, body, comments and tags")
            )
        )
    );

    // 3. Loop inside .Fields to add fields
    var fieldExpressions = new Expression<Func<Post, object>>[]
    {
        f => f.Title,
        f => f.Body,
        f => f.Comments,
        f => f.Tags
    };

    searchResponse = client.Search<Post>(m => m
        .Query(q => q
            .QueryString(qs => qs
                .Fields(f =>
                {
                    foreach (var field in fieldExpressions)
                        f.Field(field);
                        
                    return f;
                })
                .Query("search for this in post title, body, comments and tags")
            )
        )
    );

    // 4. use the Object Initializer syntax to build a searchrequest instance
    var searchRequest = new SearchRequest<Post>
    {
        Query = new QueryStringQuery
        {
            Fields = new []
            {
                Infer.Field<Post>(f => f.Title),
                Infer.Field<Post>(f => f.Body),
                Infer.Field<Post>(f => f.Comments),
                Infer.Field<Post>(f => f.Tags)
            },
            Query = "search for this in post title, body, comments and tags"
        }
    };

    searchResponse = client.Search<Post>(searchRequest);
}

public class Post
{
    public string Title { get; set; }

    public string Body { get; set; }

    public IEnumerable<string> Comments { get; set; }

    public IEnumerable<string> Tags { get; set; }
}