using System;

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

​

public class Response

{

  public string ReturnCode { get; set; }

  public JObject Data { get; set; }

  public string Message { get; set; }

  public string ErrorGuid { get; set; }

}

​

public class Program

{

    public static void Main()

    {

        var responseStr = "{\"ReturnCode\": \"Error\", \"Data\": { \"Order is Closed\": \"CannotShip\" }, \"Message\": null, \"ErrorGuid\": null }";

        var response = JsonConvert.DeserializeObject<Response>(responseStr);

        Console.WriteLine(response.Data);

    }

}