Handling JSON single object and array

Question

I'm using Newtonsoft.Json to work with some JSON data that is being returned to me. Depending on what I request I can either get back something that looks like:

{
"TotalRecords":2,
"Result":
    [
        {
        "Id":24379,
        "AccountName":"foo"
        },
        {
        "Id":37209,
        "AccountName":"bar"
        }
    ],
"ResponseCode":0,
"Status":"OK",
"Error":"None"
}

or

{
    "Result":
    {
        "Id":24379,
        "AccountName":"foo"
    },
    "ResponseCode":0,
    "Status":"OK",
    "Error":"None"
}

So sometimes "Result" is an array of Results or "Result" could be a single response.

I've tried using the answer from How to handle both a single item and an array for the same property using JSON.net but I still get errors.

In particular I'm getting a

Newtonsoft.json.jsonSerializationException: 'Cannot deserialize the current JSON object (e.g. {"name":"value"}) into type 'System.Collections.Generic.List'...

Custom converter looks like:

public class SingleOrArrayConverter<T> : JsonConverter
    {
        public override bool CanConvert(Type objecType)
        {
            return (objecType == typeof(List<T>));
        }

        public override object ReadJson(JsonReader reader, Type objecType, object existingValue,
            JsonSerializer serializer)
        {
            JToken token = JToken.Load(reader);
            if (token.Type == JTokenType.Array)
            {
                return token.ToObject<List<T>>();
            }
            return new List<T> { token.ToObject<T>() };
        }

        public override bool CanWrite
        {
            get { return false; }
        }

        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
        {
            throw new NotImplementedException();
        }
    }

My response class(es) look like

public class TestResponse
    {
        [JsonProperty("Result")]
        [JsonConverter(typeof(SingleOrArrayConverter<string>))]
        public List<DeserializedResult> Result { get; set; }
    }
public class DeserializedResult
    {
        public string Id { get; set; }
        public string AccountName { get; set; }
    }

And finally my request looks like

List<TestResponse> list = JsonConvert.DeserializeObject<List<TestResponse>>(response.Content);

They'll only ever follow one of those two formats, though the content will obviously be different. Sometimes "Result" will have several fields, other times only one or two regardless of if it returns a single object or an array of up to 100 objects. — gilliduck, May 21 '17 at 18:43

Maria Ines Parnisari · Accepted Answer · 2017-05-21T19:29:53.543

14

Your code is fine, it just needs a few type tweaks.

This line

List<TestResponse> list = JsonConvert.DeserializeObject<List<TestResponse>>(response.Content);

needs to be like this, because your response is an object, not a List.

TestResponse list = JsonConvert.DeserializeObject<TestResponse>(response);

Then your custom deserializer attribute:

[JsonConverter(typeof(SingleOrArrayConverter<string>))]

needs to become:

[JsonConverter(typeof(SingleOrArrayConverter<DeserializedResult>))]

because your Result object is not a string or an array of strings, it's either an array of DeserializedResults or a DeserializedResult.

edited May 21 '17 at 19:29

answered May 21 '17 at 19:04

Maria Ines Parnisari

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1

I owe you a beer (or whatever you drink). I'm kicking myself that it was such as minor tweak to get it working. A thousand thanks! – gilliduck May 21 '17 at 19:43
1

It just saved my day :) – Paulo Honório Jan 29 '19 at 13:04
1

Thanks. This was of great help. – Arun Gupta Oct 20 '19 at 05:45

score 0 · Answer 2 · answered May 21 '17 at 19:03

I think, that there is no way to understend which type of response do you have due desirialization. Thats why i propose to check manualy type of response:

using System;
using System.Collections.Generic;
using Newtonsoft.Json;

namespace TestConsoleApp
{
    public class Class1
    {

        public class Result
        {
            public int Id { get; set; }
            public string AccountName { get; set; }
        }

        public class ModelWithArray
        {
            public int TotalRecords { get; set; }
            public List<Result> Result { get; set; }
            public int ResponseCode { get; set; }
            public string Status { get; set; }
            public string Error { get; set; }
        }

        public class Result2
        {
            public int Id { get; set; }
            public string AccountName { get; set; }
        }

        public class ModelWithoutArray
        {
            public Result2 Result { get; set; }
            public int ResponseCode { get; set; }
            public string Status { get; set; }
            public string Error { get; set; }
        }

        public static void Main(params string[] args)
        {
            //string json = "{\"TotalRecords\":2,\"Result\":[{\"Id\":24379,\"AccountName\":\"foo\"},{\"Id\":37209,\"AccountName\":\"bar\"}], \"ResponseCode\":0,\"Status\":\"OK\",\"Error\":\"None\"}";
            string json = "{\"Result\":{\"Id\":24379,\"AccountName\":\"foo\"},\"ResponseCode\":0,\"Status\":\"OK\",\"Error\":\"None\"}";

            if (checkIsArray(json))
            {
                ModelWithArray data = JsonConver.DeserializeObject<ModelWithArray >(json);
            }else
            {
                ModelWithoutArray data = JsonConver.DeserializeObject<ModelWithoutArray>(json);
            }

        }

        static bool checkIsArray(string json)
        {

            Dictionary<string, object> desData = JsonConvert.DeserializeObject<Dictionary<string, object>>(json);

            if (desData["Result"].GetType().Name.Contains("Array"))
            {
                return true;
            }
            else
            {
                return false;
            }

        }

    }
}

`i propose to check manualy type of response`. you don't have to, the package `newtonsoft.json` provides ways of avoiding this. — Maria Ines Parnisari, May 21 '17 at 19:18

Handling JSON single object and array

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