C# demo to consume LimeSurvey API based on https://manual.limesurvey.org/RemoteControl_2_API#NodeJS_example

LimeSurveyApiTest.cs

using Newtonsoft.Json;
using System;
using System.Net.Http;
using System.Text;

namespace LimeSurveyApiTest
{
    class Program
    {
        private static readonly HttpClient client = new HttpClient();

        static void Main(string[] args)
        {
            var url = "http://PATH_OF_YOUR_SERVER/index.php/admin/remotecontrol";

            var getSessionKeyJson = JsonConvert.SerializeObject(new { method = "get_session_key", @params = new[] { "YOUR_USERNAME", "YOUR_PASSWORD" }, id = 1 });

            var getSessionKeyContent = new StringContent(getSessionKeyJson, Encoding.UTF8, "application/json");

            var getSessionKeyResponse = client.PostAsync(url, getSessionKeyContent).Result;

            if (getSessionKeyResponse.IsSuccessStatusCode)
            {
                var getSessioneyResult = getSessionKeyResponse.Content.ReadAsStringAsync().Result;
                var sessionKey = JsonConvert.DeserializeAnonymousType(getSessioneyResult, new { result = "" }).result;

                var getSurveyJson = JsonConvert.SerializeObject(new { method = "list_surveys", @params = new[] { sessionKey }, id = 1 });
                var getSurveyContent = new StringContent(getSurveyJson, Encoding.UTF8, "application/json");
                var getSurveyResponse = client.PostAsync(url, getSurveyContent).Result;
                var surveys = getSurveyResponse.Content.ReadAsStringAsync().Result;

                if (getSurveyResponse.IsSuccessStatusCode)
                {
                    Console.WriteLine($"Response: {surveys}");
                }
                else
                {
                    Console.WriteLine($"List Surveys: {getSurveyResponse.StatusCode}");
                }

            }
            else
            {
                Console.WriteLine($"Get Session Key: {getSessionKeyResponse.StatusCode}");
            }

            Console.WriteLine("End.");
            Console.ReadLine();
        }
    }
}

Hi miguelerm,
When I execute this line : "var sessionKey = JsonConvert.DeserializeAnonymousType(getSessioneyResult, new { result = "" }).result;", I receive this error:
HResult=-2146233088
LineNumber=0
LinePosition=0
Message=Unexpected character encountered while parsing value: <. Path '', line 0, position 0.
Path=""
Source=Newtonsoft.Json