Simple Usage of C# with ElasticSearch

Connection

If you don't want to expose the password, you can create your own AuthorizationHeader and use only the Base64 encoded Basic authentication key.

using Elastic.Clients.Elasticsearch;
using Elastic.Transport;

public class Program
{
    public class Base64Auth : AuthorizationHeader
    {
        private readonly string _base;
        public Base64Auth(string baseStr)
        {
            _base = baseStr;
        }
        public override string AuthScheme => "Basic";

        public override bool TryGetAuthorizationParameters(out string value)
        {
            value = _base;
            return true;
        }
    }
    static async Task Main()
    {
        var settings = new ElasticsearchClientSettings(new Uri("http://192.168.111.111:9200"))
            .Authentication(new Base64Auth("1111111111="))
            // Execute after successful connection
            .OnRequestCompleted(handler =>
            {

            });
        var client = new ElasticsearchClient(settings);
        
    }
}

Or use username and password.

            .Authentication(new BasicAuthentication("elastic", "12345"));

Method to convert username and password to Base64:

Convert.ToBase64String(Encoding.UTF8.GetBytes($"{username}:{password}"))

Inserting Documents

Insert a document into a specified index. If the index does not exist, it will be created automatically.

... ...
        var client = new ElasticsearchClient(settings);
        var tweet = new Tweet
        {
            Id = 1,
            User = "stevejgordon",
            PostDate = new DateTime(2009, 11, 15),
            Message = "Trying out the client, so far so good?"
        };

        var response = await client.IndexAsync(tweet, request => request.Index("my-tweet-index"));
        if (response.IsValidResponse)
        {
            Console.WriteLine($"Index document with ID {response.Id} succeeded.");
        }
    }
    public class Tweet
    {
        public int Id { get; set; }
        public string User { get; set; }
        public DateTime PostDate { get; set; }
        public string Message { get; set; }
    }

Retrieving Documents

Retrieve the document that was just inserted:

        var response = await client.GetAsync<Tweet>(1, idx => idx.Index("my-tweet-index"));
        var tweet = response.Source;

Use Lambda to search for documents and paginate:

        var client = new ElasticsearchClient(settings);
        var response = await client.SearchAsync<Tweet>(s => s
            .Index("my-tweet-index")
            .From(0)
            .Size(10)
            .Query(q => q
                .Term(t => t.User, "stevejgordon")
            )
        );

        if (response.IsValidResponse)
        {
            var tweet = response.Documents.FirstOrDefault();
        }

Or use the JSON format for the search method:

        var client = new ElasticsearchClient(settings);
        var request = new SearchRequest("my-tweet-index")
        {
            From = 0,
            Size = 10,
            Query = new TermQuery("user") { Value = "stevejgordon" }
        };

        var response = await client.SearchAsync<Tweet>(request);

        if (response.IsValidResponse)
        {
            var tweet = response.Documents.FirstOrDefault();
        }

Updating

Update a document with the specified Id:

        Tweet tweet = new Tweet
        {
            Id = 1,
            User = "stevejgordon",
            PostDate = new DateTime(2009, 11, 15),
            Message = "Trying out the client, so far so good?"
        };
        tweet.Message = "This is a new message";

        var response = await client.UpdateAsync<Tweet, object>("my-tweet-index", 1, u => u
                .Doc(tweet));

        if (response.IsValidResponse)
        {
            Console.WriteLine("Update document succeeded.");
        }

Deleting Documents

        var response = await client.DeleteAsync("my-tweet-index", 1);

        if (response.IsValidResponse)
        {
            Console.WriteLine("Delete document succeeded.");
        }