Newtosoft，PCL和Xamarin.Droid

Question

I'am facing to a strange problem.

I have a generic code that's was in my PCL project. This code is currently perferctly working in my windows phone project, but not in the android one.

Here the code : ( the method that have the problem is CreateListFriend )

public class Friend : IFriend<User>
    {
        public int Id { get; set; }
        public string UserId { get; set; }
        public virtual User User { get; set; }

        private static volatile Friend instance;
        private static object syncRoot = new Object();

        private Friend() { }

        public static Friend Instance
        {
            get
            {
                if (instance == null)
                {
                    lock (syncRoot)
                    {
                        if (instance == null)
                            instance = new Friend();
                    }
                }

                return instance;
            }
        }


        /// <summary>
        /// Populate friend instance
        /// </summary>
        /// <param name="json">Json friend string</param>
        public void PopulateFriend(string json)
        {
            if (!String.IsNullOrEmpty(json))
            {
                var resultObj = JsonConvert.DeserializeObject<Friend>(json);
                Friend.Instance.Id = resultObj.Id;
                Friend.Instance.UserId = resultObj.UserId;
            }
        }

        /// <summary>
        /// Create friend list from json
        /// </summary>
        /// <param name="json">json string</param>
        /// <returns>friend list</returns>
        public List<Friend> CreateListFriend(string json)
        {
            List<Friend> resultObj = new List<Friend>();
            if (!String.IsNullOrEmpty(json))
            {
                resultObj = JsonConvert.DeserializeObject<List<Friend>>(json);
            }

            return resultObj;

        }
    }

As you can see in the previous picture, Json.net is able to "deserialize" but the object friend donc have the correct "fields"....

I already tried to supress the class and recreate it... I already created a structure with the same fields, and all json deserialize it correctly, but i don't want to do it by this way.

Is somebody have an idea...

Answer 1

Let's assume we have two JSON source file:

friend.json:

{
    "id": 5,
    "userId": 6
}

friends.json:

[
    {
        "id": 1,
        "userId": 2
    },
    {
        "id": 2,
        "userId": 3
    },
    {
        "id": 3,
        "userId": 4
    },
    {
        "id": 4,
        "userId": 5
    }
]

We also have the Friend class. Based on your example your class is a POCO for Entity Framework. JsonProperty attribute is not needed if the source file has the same property names as your class.

Note: I did not define any constructor for Friend class so it will have only one public parameterless constructor by default.

public class Friend
{
    [JsonProperty("id")]
    public int Id { get; set; }

    [JsonProperty("userId")]
    public string UserId { get; set; }

    public virtual User User { get; set; }

    public override string ToString()
    {
        return String.Format("User: Id={0}; UserId={1}", Id, UserId);
    }
}

I would separate the logic for creating Friend instances. Just for an example I create a FriendLoader class.

public class FriendLoader
{
    public Friend LoadFriend(string jsonSource)
    {
        return String.IsNullOrEmpty(jsonSource) ? null : JsonConvert.DeserializeObject<Friend>(jsonSource);
    }

    public List<Friend> LoadFriends(string jsonSource)
    {
        var friends = new List<Friend>();

        if (!String.IsNullOrEmpty(jsonSource))
        {
            friends = JsonConvert.DeserializeObject<List<Friend>>(jsonSource);
        }

        return friends;
    }
}

Here is the console app to test the above code.

class Program
{
    static void Main(string[] args)
    {
        string friendJson = File.ReadAllText("friend.json");
        string friendsJson = File.ReadAllText("friends.json");

        var loader = new FriendLoader();

        var friend = loader.LoadFriend(friendJson);
        var friends = loader.LoadFriends(friendsJson);

        Console.WriteLine("One friend:");
        Console.WriteLine(friend);

        Console.WriteLine();

        Console.WriteLine("List of friends:");
        friends.ForEach(Console.WriteLine);
    }
}

Hope this helps.

By the way, could you please show the definition of your IFriend<T> interface?

Answer 2

sorry for the delay I did not have the time this week to post.

This is not related to my class but to the android.platform.

We just need to tell android platform to preserve all attribute with this :

[Preserve(AllMembers = true)]

Thanks for your time :)