作者使用的NEST版本7.11.1
官方文档https://www.elastic.co/guide/en/elasticsearch/client/net-api/7.x/nest-getting-started.html

测试API类代码

using Nest;
using System;
using System.Collections.Generic;

namespace TestAPI.Models
{
    public class StudentAPI
    {
        private ElasticClient _client;
        public static string ConnectionSettings = "http://192.168.1.156:9200";

        public static string IndexName = "student";

        private static int _size = 20;
        public StudentAPI() 
        {
            var settings = new ConnectionSettings(new Uri(ConnectionSettings))
                        .DefaultIndex(IndexName);
            _client = new ElasticClient(settings);
        }
        /// <summary>
        /// 创建索引
        /// </summary>
        /// <returns></returns>
        public bool CreateIndex() {

            try
            {
                dynamic response = _client.Indices.Get(IndexName);
                if (!response.IsValid)
                {
                    response = _client.Indices.Create(IndexName, c => c
                    .Map<Student>(m => m
                        .AutoMap()
                    ));
                    Console.WriteLine(response);
                }
                return true;
            }
            catch (Exception e)
            {
                return false;
                throw;
            }
        }

        /// <summary>
        /// 删除索引
        /// </summary>
        /// <returns></returns>
        public bool DeleteIndex() 
        {
            try
            {
                //根据名称删除索引
                var response = _client.Indices.Delete(IndexName);
                return true;
            }
            catch (Exception)
            {

                throw;
            }
        }
        /// <summary>
        /// 添加文档
        /// </summary>
        /// <param name="stu"></param>
        /// <returns></returns>
        public bool Add(Student stu) 
        {
            try
            {

                var indexResponse = _client.Index(stu, i => i.Index(IndexName).Id(stu.ID));

                if (!indexResponse.IsValid)
                {
                    // If the request isn't valid, we can take action here
                    return false;
                }
                return true;
            }
            catch (Exception e)
            {
                return false;
                throw;
            }
        }
        /// <summary>
        /// 批量添加文档
        /// </summary>
        /// <param name="lists"></param>
        /// <returns></returns>
        public bool BulkDescriptor(List<Student> lists)
        {
            try
            {
                //批量创建文档
                BulkDescriptor descriptor = new BulkDescriptor();
                for (int i = 0; i < lists.Count; i++)
                {
                    var stu = lists[i];
                    descriptor.Index<Student>(op => op.Document(stu).Index(IndexName).Id(stu.ID));
                }

                var response = _client.Bulk(descriptor);
                return true;
            }
            catch (Exception)
            {

                throw;
            }
        }
        /// <summary>
        /// 根据ID删除文档
        /// </summary>
        /// <param name="id"></param>
        /// <returns></returns>
        public bool Delete(string id) 
        {
            try
            {
                //根据特定的条件来删除文档
                var response = _client.Delete<Student>(id, d => d.Index(IndexName));

                //删除文档
                //response = _client.Delete<Student>(id.CompanyID);
                return true;
            }
            catch (Exception)
            {

                throw;
            }
        }
        /// <summary>
        /// 更新文档
        /// </summary>
        /// <param name="stu"></param>
        /// <returns></returns>
        public bool Updelete(Student stu) 
        {
            try
            {
                var response = _client.Index(stu, i => i.Id(stu.ID));
                //修改指定版本的文档
                //response = _client.Index(stu, i => i.Id(stu.CompanyID).Version(1));
                return true;
            }
            catch (Exception)
            {
                throw;
                return false;
            }
        }

        
        /// <summary>
        /// 获取索引中所有文档
        /// </summary>
        /// <returns></returns>
        public IReadOnlyCollection<Student> GetAll()
        {
            try
            {

                var str = "";
                var searchResponse = _client.Search<Student>(s => s
                    .Index(IndexName)
                    .Query(q => q
                        .MatchAll()
                    )
                );

                return searchResponse.Documents;
            }
            catch (Exception e)
            {
                return null;
                throw;
            }
            
        }
        /// <summary>
        /// 分页查询，keyword过滤所有字段
        /// </summary>
        /// <param name="keyword"></param>
        /// <param name="page"></param>
        /// <returns></returns>
        public IReadOnlyCollection<Student> GetAllField(string keyword, int page)
        {
            try
            {
                var searchAll = _client.Search<Student>(s => s
                    .Index(IndexName)
                    .From(page)
                    .Size(_size)
                    .Query(q => q
                        .QueryString(qs => qs
                            .Query(keyword).DefaultOperator(Operator.And))
                        ));

                return searchAll.Documents;
            }
            catch (Exception)
            {

                throw;
            }
        }
        /// <summary>
        /// 分页查询，根据Name获取文档
        /// </summary>
        /// <param name="keyword"></param>
        /// <param name="page"></param>
        /// <returns></returns>
        public IReadOnlyCollection<Student> GetByName(string keyword,int page)
        {
            try
            {
                var searchResponse = _client.Search<Student>(s => s
                     .Index(IndexName)
                     .From(page)
                     .Size(_size)
                     .Query(q => q
                        .Match(m => m
                            .Field(
                                f => f.Name
                            )
                            .Query(keyword))
                        ));

                return searchResponse.Documents;
            }
            catch (Exception)
            {

                throw;
            }
        }
        /// <summary>
        /// 查询所有，选择Name，ID，Age，三个字段输出数据
        /// </summary>
        /// <returns></returns>
        public IReadOnlyCollection<Student> GetSelectFields()
        {
            try
            {

                var searchResponse = _client.Search<Student>(s => s
                    .Index(IndexName)
                    .Source(fs => fs
                        .Includes(fh => fh   //包含以下字段
                            .Fields(
                                f => f.Name,
                                f => f.ID,
                                f => f.Age
                            )
                        )
                        .Excludes(e => e    //排除以下字段
                            .Fields(   
                                f => f.Birthday,
                                f => f.IsManager
                            )   
                        )
                    )
                    .Query(q => q
                        .MatchAll()
                    )
                );

                return searchResponse.Documents;
            }
            catch (Exception)
            {

                throw;
            }
        }
        /// <summary>
        /// 分页查询，根据Name，Birthday字段
        /// </summary>
        /// <param name="keyword"></param>
        /// <param name="sdate"></param>
        /// <param name="edate"></param>
        /// <param name="page"></param>
        /// <returns></returns>
        public IReadOnlyCollection<Student> GetByNameAndDay(string keyword, DateTime sdate, DateTime edate, int page)
        {
            try
            {
                var searchResponse = _client.Search<Student>(s => s
                    .Index(IndexName)
                    .From(page)
                    .Size(_size)
                    .Query(q => q
                        .Bool(b => b
                            .Must(mu => mu
                                .Match(m => m
                                    .Field(f => f.Name)
                                    .Query(keyword)
                                )
                            )
                            .Filter(fi => fi
                                 .DateRange(r => r
                                    .Field(f => f.Birthday)
                                    .GreaterThanOrEquals(sdate)
                                    .LessThan(edate)
                                )
                            )
                        )
                    )
                );

                另一个写法
                //var searchResponse = _client.Search<Project>(s => s
                //    .Query(q => q
                //        .Match(m => m
                //            .Field(f => f.FirstName)
                //            .Query("许")
                //        ) && q
                //        .Match(m => m
                //            .Field(f => f.LastName)
                //            .Query("嵩")
                //        ) && +q
                //        .DateRange(r => r
                //            .Field(f => f.StartedOn)
                //            .GreaterThanOrEquals(new DateTime(2017, 01, 01))
                //            .LessThan(new DateTime(2018, 01, 01))
                //        )
                //    )
                //);

                return searchResponse.Documents;
            }
            catch (Exception)
            {

                throw;
            }
        }
    }
}

linux中发布.net core api参考：
链接: https://www.jianshu.com/p/5fda6340ce22.