using System;

using System.IO;

using Newtonsoft.Json;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var json = "{ \"x\": {\"a\":1 }, \"y\": {\"b\":2 } }";

        var dict = JsonConvert.DeserializeObject<Dictionary<string, object>>(json);

        foreach (var key in dict.Keys) 

        {

            Console.WriteLine(key);

        }   

    }

}