NEST mapping, index only the first name

elasticHelloWorld.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace TestIndex
{
    using Nest;

    class Program
    {
        static void Main(string[] args)
        {
            var node = new Uri("http://localhost:9200");

            var settings = new ConnectionSettings(
                node,
                defaultIndex: "test"
            );

            var client = new ElasticClient(settings);

            client.Map<Person>(m =>
                m.IdField(f => f.Path("id"))
                .IncludeInAll(false)
                .SourceField(s=>s.Excludes(new []{"lastname"}))
                .Properties(p =>
                    p.String(s => s.Name(n => n.Firstname).Analyzer("standard").Index(FieldIndexOption.Analyzed).Store(false))
                    //.String(s => s.Name(n => n.Lastname).Analyzer("standard").Index(FieldIndexOption.Analyzed).Store())
                   // .Object<string>(x=>x.Enabled(false).Name(n=>n.Lastname))
                    )
                );

            var person = new Person
            {
                Id = "3",
                Firstname = "bob",
                Lastname = "rundle"
            };

            var index = client.Index(person);


            var result = client.Search<Person>(s => s.Query(q => q.Term(p => p.Firstname, "bob")).Fields(p=>p.Id));

            var id = result.Hits.First().Fields.FieldValues<string[]>("id").First();
            
        }
    
    }

    public class Person
    {
        public string Id { get; set; }
        public string Firstname { get; set; }
        public string Lastname { get; set; }
    }
}