Elasticsearch client for C# (.NET): NEST and Elastic.Clients.Elasticsearch

Elasticsearch client for C# (.NET): NEST and Elastic.Clients.Elasticsearch

Elasticsearch is a powerful distributed search and analytics system based on Apache Lucene. To work with it from C# (.NET) applications, there are several official and third-party clients. In this article, we will take a detailed look at two main libraries: NEST (high-level client) and Elastic.Clients.Elasticsearch (new official client from Elastic). You will learn how to install, configure, and use them for indexing, searching, and data management.

1. NEST — high-level client (recommended for complex projects)

NEST is an old but proven client that provides a strongly typed API using POCO classes. It automatically serializes/deserializes JSON to C# objects and supports fluent syntax for building queries.

Installation

dotnet add package NEST

Example of using NEST

using Nest;using System;

// POCO class for the documentpublic class Article{    public int Id { get; set; }    public string Title { get; set; }    public string Content { get; set; }    public DateTime PublishDate { get; set; }}

class Program{    static async Task Main(string[] args)    {        // Connection setup        var settings = new ConnectionSettings(new Uri("http://localhost:9200"))            .DefaultIndex("articles")            .EnableDebugMode(); // Enable request logging

        var client = new ElasticClient(settings);

        // 1. Indexing a document        var article = new Article        {            Id = 1,            Title = "Elasticsearch in C#",            Content = "Detailed guide on working with Elasticsearch from .NET",            PublishDate = DateTime.UtcNow        };

        var indexResponse = await client.IndexDocumentAsync(article);        Console.WriteLine($"Indexing: {indexResponse.IsValid}");

        // 2. Search        var searchResponse = await client.SearchAsync<Article>(s => s            .Query(q => q                .Match(m => m                    .Field(f => f.Title)                    .Query("Elasticsearch")                )            )        );

        foreach (var hit in searchResponse.Hits)        {            Console.WriteLine($"Found: {hit.Source.Title}");        }    }}

2. Elastic.Clients.Elasticsearch — new official client

Starting with version 8.x, Elastic released a new client Elastic.Clients.Elasticsearch (also known as Elasticsearch.Net). It is lighter, asynchronous, and compliant with the latest versions of Elasticsearch. Unlike NEST, it does not require mandatory use of POCO classes, although it supports them.

Installation

dotnet add package Elastic.Clients.Elasticsearch

Example of using the new client

using Elastic.Clients.Elasticsearch;using Elastic.Clients.Elasticsearch.QueryDsl;using System;

class Program{    static async Task Main(string[] args)    {        // Connection setup        var settings = new ElasticsearchClientSettings(new Uri("http://localhost:9200"))            .DefaultIndex("articles");

        var client = new ElasticsearchClient(settings);

        // 1. Indexing with POCO        var article = new Article        {            Id = 2,            Title = "New Elasticsearch client",            Content = "Overview of Elastic.Clients.Elasticsearch capabilities",            PublishDate = DateTime.UtcNow        };

        var indexResponse = await client.IndexAsync(article, idx => idx.Index("articles"));        Console.WriteLine($"Indexing: {indexResponse.IsValidResponse}");

        // 2. Search using lambda syntax        var se