using System;

using System.Net.Http;

using System.Net.Http.Headers;

using System.Threading.Tasks;

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

public class Program

{

    public static void Main()

    {

            string api_key  = "cf3a86511d24c617aa6225ab0b685abdaa5f4eb6b9eb67bf";

            string requtext = "туман";

            var url         = "https://textorobot.ru/api/synonymize?apiKey=" + api_key + "&text=" + requtext;

        var client = new HttpClient();

        var request = new HttpRequestMessage()

        {

            Method = new HttpMethod("GET"),

            RequestUri = new Uri(url),

        };

        var response = Task.Run(() => client.SendAsync(request)).Result;

        var content = response.Content.ReadAsStringAsync().Result;

            var jo = JObject.Parse(content);

            var jsontext = jo["data"]["processedText"].ToString();

            Console.WriteLine(jsontext);

    }

}