Using Newtonsoft.Json with RestSharp v106.6

JsonNetRestSharp.cs

using Newtonsoft.Json;
using RestSharp;
using RestSharp.Serialization;

namespace JsonNetRestSharp
{
    class Program
    {
        static void Main(string[] args)
        {
            var client = new RestClient("https://my.api.com")
                .UseSerializer(new JsonNetSerializer());
        }

        public class JsonNetSerializer : IRestSerializer
        {
            public string Serialize(object obj) => 
                JsonConvert.SerializeObject(obj);

            public string Serialize(BodyParameter bodyParameter) => 
                JsonConvert.SerializeObject(bodyParameter.Value);

            public T Deserialize<T>(IRestResponse response) => 
                JsonConvert.DeserializeObject<T>(response.Content);

            public string[] SupportedContentTypes { get; } =
            {
                "application/json", "text/json", "text/x-json", "text/javascript", "*+json"
            };

            public string ContentType { get; set; } = "application/json";

            public DataFormat DataFormat { get; } = DataFormat.Json;
        }
    }
}