Cannot deserialize JSON array into type - Json.NET

Question

I am trying to deserialize a json data into a model class but I am failing. Here is what I do:

 public CountryModel GetCountries() { using (WebClient client = new WebClient()) { var result = client.DownloadString("http://api.worldbank.org/incomeLevels/LIC/countries?format=json"); var output = JsonConvert.DeserializeObject<List<CountryModel>>(result); return output.First(); } } 

This is how my model looks like:

public class CountryModel { public int Page { get; set; } public int Pages { get; set; } public int Per_Page { get; set; } public int Total { get; set; } public List<Country> Countries { get; set; } } public class Country { public int Id { get; set; } public string Iso2Code { get; set; } public string Name { get; set; } public Region Region { get; set; } } public class Region { public int Id { get; set; } public string Value { get; set; } } 

You can see the Json I am getting here: http://api.worldbank.org/incomeLevels/LIC/countries?format=json

This is the error I get:

Cannot deserialize JSON array into type 'Mvc4AsyncSample.Models.CountryModel'. Line 1, position 1.

Answer 1

You have to write a custom JsonConverter:

 public class CountryModelConverter : JsonConverter { public override bool CanConvert(Type objectType) { if (objectType == typeof(CountryModel)) { return true; } return false; } public override object ReadJson(JsonReader reader, Type objectType , object existingValue, JsonSerializer serializer) { reader.Read(); //start array //reader.Read(); //start object JObject obj = (JObject)serializer.Deserialize(reader); //{"page":1,"pages":1,"per_page":"50","total":35} var model = new CountryModel(); model.Page = Convert.ToInt32(((JValue)obj["page"]).Value); model.Pages = Convert.ToInt32(((JValue)obj["pages"]).Value); model.Per_Page = Int32.Parse((string) ((JValue)obj["per_page"]).Value); model.Total = Convert.ToInt32(((JValue)obj["total"]).Value); reader.Read(); //end object model.Countries = serializer.Deserialize<List<Country>>(reader); reader.Read(); //end array return model; } public override void WriteJson(JsonWriter writer, object value , JsonSerializer serializer) { throw new NotImplementedException(); } } 

And tag the CountryModel with that converter (I also had to switch some int to string):

 [JsonConverter(typeof(CountryModelConverter))] public class CountryModel { public int Page { get; set; } public int Pages { get; set; } public int Per_Page { get; set; } public int Total { get; set; } public List<Country> Countries { get; set; } } public class Country { public string Id { get; set; } public string Iso2Code { get; set; } public string Name { get; set; } public Region Region { get; set; } } public class Region { public string Id { get; set; } public string Value { get; set; } } 

Then you should be able to deserialize like this:

var output = JsonConvert.DeserializeObject<CountryModel>(result); 

Answer 2

This looks like a (not very good) attempt at representing XML in JSON. The JSON looks like this:

[ { "page": 1, … }, [ { "id": "AFG", "name": "Afghanistan", … }, { "id": "BDI", "name": "Burundi", … }, … ] ] 

While a reasonable JSON (that would incidentally map to your model nicely) would look like this:

{ "page": 1, …, "countries": [ { "id": "AFG", "name": "Afghanistan", … }, { "id": "BDI", "name": "Burundi", … }, … ] } 

If you are sure you want to use JSON (and not XML), you can do it by first deserializing the JSON into JSON.NET's object model and then deserialize that into your model:

var json = client.DownloadString("http://api.worldbank.org/incomeLevels/LIC/countries?format=json"); var array = (JArray)JsonConvert.DeserializeObject(json); var serializer = new JsonSerializer(); var countryModel = serializer.Deserialize<CountryModel>(array[0].CreateReader()); countryModel.Countries = serializer.Deserialize<List<Country>>(array[1].CreateReader()); return countryModel; 

Don't forget to change your Id properties to string, because that's what they are.

Answer 3

Your model doesn't match the JSON structure. It looks like your missing the last 6 properties.

{ "id": "AFG", "iso2Code": "AF", "name": "Afghanistan", "region": { "id": "SAS", "value": "South Asia" }, "adminregion": { "id": "SAS", "value": "South Asia" }, "incomeLevel": { "id": "LIC", "value": "Low income" }, "lendingType": { "id": "IDX", "value": "IDA" }, "capitalCity": "Kabul", "longitude": "69.1761", "latitude": "34.5228" 

}