using System;

using Newtonsoft.Json;

public class Program

{

    public class AccountInfo

    {

        [JsonProperty("@IDTypeCode")]

        public string IDTypeCode {get; set;}

        [JsonProperty("@SystemCode")]

        public string SystemCode {get; set;}

        public string IDValue {get; set;}

    }

    public class Message

    {

        public AccountInfo AccountID {get; set;}

    }

    public static void Main()

    {

        var msg = @"

             {

            ""AccountID"": {

                ""@IDTypeCode"": ""Account"",

                ""@SystemCode"": ""SAP"",

                ""IDValue"": ""0830482378""

                }

              }";

        var deserialized = JsonConvert.DeserializeObject<Message>(msg);

        ObjectDumper.Dumper.Dump(deserialized,"Message", Console.Out);

    }

}