using System;

using System.Collections.Generic;

using Newtonsoft.Json;

public class Program

{

    public static void Main()

    {

        const string json = @"{ 

            ""TEstId"": 179, 

            ""OrderChanges"": [ 

                { 

                    ""item1"": 12, 

                    ""item2"": [ 10 ] 

                }, 

                { 

                    ""item1"": 42, 

                    ""item2"": [ 1, 2, 3 ] 

                } 

            ] 

        }";

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

        Console.WriteLine("ID: {0}", result.TEstId);

        Console.WriteLine("Order changes:");

        foreach (var item in result.OrderChanges)

        {

            Console.WriteLine("- {0} = [{1}]", item.issueId, string.Join(", ", item.newChildIds));

        }

        string serialized = JsonConvert.SerializeObject(result);

        Console.WriteLine(serialized);

    }

}

​

class Test

{

    public long TEstId{ get; set; }

    public IEnumerable<(long? issueId, long[] newChildIds)> OrderChanges { get; set; }

}