C# NEST 客户端 访问 Elasticsearch服务器 BlogMoreLikeThis

1.GUI方面：有像kopf之类的Plugin可以用。
2.自己写程序操作接RESTFUL Api
3.通过浏览器访问
4.客户端Elasticsearch .NET：像是连Stack Overflow都使用的NEST。

关系数据库      ⇒ 数据库        ⇒  表         ⇒ 行              ⇒ 列(Columns)
 
Elasticsearch  ⇒ 索引(Index)   ⇒ 类型(type)  ⇒ 文档(Docments)  ⇒ 字段(Fields)  

namespace Nop.Web.Components
{
    //----new 20210511

    [ViewComponent(Name = "BlogMoreLikeThis")]
    public class BlogMoreLikeThisViewComponent : ViewComponent
    {
        #region Fields
        readonly IConfiguration _configuration;

        #endregion

        public BlogMoreLikeThisViewComponent(IConfiguration configuration)
        {
            _configuration = configuration;
        }
        public async Task<IViewComponentResult> InvokeAsync(string query)
        {
            SearchViewModel viewModel = new SearchViewModel();
            //如果查询字符串为空，则直接返回
            if (String.IsNullOrEmpty(query))
            {



                return View(viewModel);

            }

            try
            {

                // 1.设置

                var nodeUrl = _configuration["BlogMoreLikeThis:ConnectionString"];

                var indexName = _configuration["BlogMoreLikeThis:IndexName"];

                // var node = new Uri("http://localhost:9200"); //old
                var node = new Uri(nodeUrl);  //new

                var settings = new ConnectionSettings(node);
                // settings.DefaultIndex("wwwiaspnetcoreindex"); //old
                settings.DefaultIndex(indexName);   //new
                var client = new ElasticClient(settings);




                //获取分页参数
                int currentPageIndex = 0;
                int itemsPerPage = 10;

                string queryString = query;

                var preQueryString = client.Indices.Analyze(a => a.Index(indexName).Analyzer("ik_max_word").Text(queryString));

                if (!preQueryString.IsValid)
                    throw new ArgumentNullException("字符串分词失败");

                var queryStringLagerThanTwoHzHashSet = new HashSet<string>();

                string queryStringLagerThanTwoHz = "";
                foreach (var item in preQueryString.Tokens)
                {
                    int len = item.Token.Length;

                    if ((len >= 2) && !queryStringLagerThanTwoHz.Contains(item.Token)) //大于两个汉字且字符串中没有同样的
                    {
                        queryStringLagerThanTwoHz += item.Token + " ";
                    }
                }

                var searchResults421 = client.Search<BlogPostModel>(s => s
                  .Index(indexName)
                  .Query(q => q.QueryString(qs => qs.Query(queryString).DefaultOperator(Operator.Or)))
                  );

                var searchResults420 = client.Search<BlogPostModel>(s => s  //高亮成功，加标题，成功

             .From(currentPageIndex)
             .Size(itemsPerPage)
             .Query(q => q.QueryString(qs => qs.Query(queryString).DefaultOperator(Operator.Or)))
             .Sort(ss => ss.Descending(p => p.CreatedOn))// 加入时间排序
              .Highlight(h => h
              .PreTags("<b>")
              .PostTags("</b>")
              .Fields(f => f.Field(e => e.Body).PreTags("<font color =\"red\">").PostTags("</font>"),
                   f => f.Field(e => e.Title).PreTags("<font color =\"red\">").PostTags("</font>")))



    );





                //返回结构用户显示
                var returnsearchResults = new Tuple<IEnumerable<IHit<BlogPostModel>>, long>(searchResults421.Hits, searchResults421.Took);


                viewModel.Results = searchResults421.Hits;
                viewModel.Elapsed = searchResults421.Took;
                viewModel.Total = searchResults421.Total;
                viewModel.Query = query;

                viewModel.Paging.CurrentPage = currentPageIndex + 1;
                viewModel.Paging.ItemsPerPage = itemsPerPage;
                viewModel.Paging.TotalItems = (int)searchResults421.Total;

                return View(viewModel);
            }
            catch (Exception ex)
            {
                return View(viewModel);
            }



        }
    }