Deserializing JSON into an object with Json.NET

Question

I'm playing a little bit with the new StackOverflow API. Unfortunately, my JSON is a bit weak, so I need some help.

I'm trying to deserialize this JSON of a User:

  {"user":{
    "user_id": 1,
    "user_type": "moderator",
    "creation_date": 1217514151,
    "display_name": "Jeff Atwood",
    ...
    "accept_rate": 100
  }}

into an object which I've decorated with JsonProperty attributes:

[JsonObject(MemberSerialization.OptIn)]
public class User
{
    [JsonProperty("user_id", Required = Required.Always)]        
    public virtual long UserId { get; set; }

    [JsonProperty("display_name", Required = Required.Always)]
    public virtual string Name { get; set; }

    ...
}

I get the following exception:

Newtonsoft.Json.JsonSerializationException: Required property 'user_id' not found in JSON.

Is this because the JSON object is an array? If so, how can I deserialize it to the one User object?

Thanks in advance!

You have two objects in this JSON. The outer object has a single property user which contains the actual user object. Are you taking this into account in your code? I also don't see any JSON arrays here. — Alex Jasmin
– Alex Jasmin, Commented Mar 31, 2010 at 18:43

Alex Jasmin · Accepted Answer · 2010-04-01 01:19:19Z

36

If you don't want to create a wrapper class you can also access the User this way:

String jsonString = "{\"user\":{\"user_id\": 1, \"user_type\": \"moderat...";
JToken root = JObject.Parse(jsonString);
JToken user = root["user"];
User deserializedUser = JsonConvert.DeserializeObject<User>(user.ToString());

See this page in the Json.NET doc for details.

edited Apr 1, 2010 at 1:19

answered Mar 31, 2010 at 19:31

Alex Jasmin

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2 Comments

Homer Over a year ago

Thanks! Used to deserialize my array of objects List<User> deserializedUsers = JsonConvert.DeserializeObject<List<User>>(users.ToString());

Bill N. Over a year ago

Thanks! This led me to fixing my issue

Jarrod Dixon · Accepted Answer · 2010-03-31 19:28:16Z

27

As Alexandre Jasmin said in the comments of your question, the resulting JSON has a wrapper around the actual User object you're trying to deserialize.

A work-around would be having said wrapper class:

public class UserResults
{
    public User user { get; set; }
}

Then the deserialization will work:

using (var sr = new StringReader(json))
using (var jr = new JsonTextReader(sr))
{
    var js = new JsonSerializer();
    var u = js.Deserialize<UserResults>(jr);
    Console.WriteLine(u.user.display_name);
}

There will be future metadata properties on this wrapper, e.g. response timestamp, so it's not a bad idea to use it!

answered Mar 31, 2010 at 19:28

Jarrod Dixon

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1 Comment

Igal Tabachnik Over a year ago

Thank you very much, Jarrod, for the explanation, and the very great solution!

Community · Accepted Answer · 2017-05-23 10:30:49Z

5

Similar to @Alexandre Jasmin's answer, you can use an intermediary JsonSerializer to convert instead of the using the high-level JsonConvert on .ToString(). No idea if it's any more efficient...

References:

Example:

var root = JObject.Parse(jsonString);
var serializer = new JsonSerializer();
var expectedUserObject = serializer.Deserialize<User>(root["user"].CreateReader());

edited May 23, 2017 at 10:30

CommunityBot

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answered Jan 25, 2013 at 17:47

drzaus

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