using System;

using Newtonsoft.Json;

public class Program

{

    public static void Main()

    {

        string koValue = "{\"CustomFieldId\":\"1\",\"AssignmentObjectId\":\"null\",\"Value\":\"\",\"Child\":null}";

        if(TryDeserialize<NestedCustomFieldNodeValueDto>(koValue, out NestedCustomFieldNodeValueDto x1))

        {

                Console.WriteLine("OK "+ x1.CustomFieldId);

        }

        else

        {

                Console.WriteLine("KO ");

        }

        string okValue = "{\"CustomFieldId\":\"2\",\"AssignmentObjectId\":\"666\",\"Value\":\"eeee\",\"Child\":null}";

        if(TryDeserialize<NestedCustomFieldNodeValueDto>(okValue, out NestedCustomFieldNodeValueDto x2))

        {

                Console.WriteLine("OK "+ x2.Value);

        }

        else

        {

                Console.WriteLine("KO ");

        }

        // exception

        var err500 = JsonConvert.DeserializeObject<NestedCustomFieldNodeValueDto>(koValue);

​

    }

    public class NestedCustomFieldNodeValueDto

    {

        public int CustomFieldId { get; set; }

        public int? AssignmentObjectId { get; set; }

        public string Value { get; set; }

        public string CodeValue { get; set; }

        public NestedCustomFieldNodeValueDto Child { get; set; }

    }

    private static bool TryDeserialize<T>(string json, out T result)

    {

        try

        {

            result = JsonConvert.DeserializeObject<T>(json);

            return true;

        }

        catch

        {

            result = default;

            return false;

        }

    }

}