Convert JSON to list of objects

Question

I have defined a Quote class like this:

public class Quote
{
    public double Price { get; set; }
    public string Symbol { get; set; }
}

The following JSON is returned by a Web API rest endpoint and does not include an explicit symbol field. The symbols are the named objects, e.g. AAPL, GOOG, FB:

{                       
    "AAPL": {           
        "price": 205    
    },                  
    "GOOG": {           
        "price": 1230.38
    },                  
    "FB": {             
        "price": 178.41 
    }                   
}

What is the best way to convert this JSON to a List<Quote>?

The json doesn't explicitly have a "symbol" field, that's the tricky part. — BaltoStar
– BaltoStar, Commented Apr 7, 2019 at 5:32
So where this symbol comes from to assign it to Symbol property in your class while deserialization — er-sho
– er-sho, Commented Apr 7, 2019 at 5:33
Where is this json object defined? any local file or is it just a string, than you want to convert to json for this Quote class? — its4zahoor
– its4zahoor, Commented Apr 7, 2019 at 5:42

er-sho · Accepted Answer · 2019-04-07 06:29:42Z

3

One simple approach to deal with your tricky part of json

1) Deserialize your json to Dictionary<string, dynamic>.

2) Then flatten your dictionary result to List<Quote>.

string json = File.ReadAllText(@"Path to your json");

List<Quote> quotes = JsonConvert.DeserializeObject<Dictionary<string, dynamic>>(json)
    .Select(x => new Quote
    {
        Symbol = x.Key,
        Price = x.Value.price    //<= x.Value is dynamic type so you can access your key with dot(.) separator
    })
    .ToList();


//-------------Print the result to Console-------------

Console.WriteLine("Symbol\tPrice");
Console.WriteLine("----------------------");
foreach (var quote in quotes)
{
    Console.WriteLine(quote.Symbol +"\t" + quote.Price);
}

Alternative:

You can use JToken instead of dynamic,

List<Quote> quotes = JsonConvert.DeserializeObject<Dictionary<string, JToken>>(json)
    .Select(x => new Quote
    {
        Symbol = x.Key,
        Price = Convert.ToDouble(x.Value["price"])
    })
    .ToList();

Output:

edited Apr 7, 2019 at 6:29

answered Apr 7, 2019 at 6:00

er-sho

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8 Comments

its4zahoor Over a year ago

That's much simpler. I want to know , is it applicable to xml format?

er-sho Over a year ago

@its4zahoor, Yes if you would like to use xml with XDocument. Because XDocument support LINQ and with LINQ you can flatten your result to whatever you want :)

BaltoStar Over a year ago

ah right i forgot about dynamic - used this years ago. but VS is giving me a method not found error for .Select - any idea why ?

er-sho Over a year ago

@BaltoStar, Add this namespace to top of your program => using System.Linq;

er-sho Over a year ago

@BaltoStar, What happen? Does it work for you? If yes then please mark the tick on left side of answer to make it green :)

|

Brian Rogers · Accepted Answer · 2019-04-07 16:18:20Z

You could make a custom JsonConverter to convert this JSON structure into the List<Quote> format you want.

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

public class QuoteListConverter : JsonConverter
{
    public override bool CanConvert(Type objectType)
    {
        return objectType == typeof(List<Quote>);
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        JObject obj = JObject.Load(reader);
        return obj.Properties()
                  .Select(p => new Quote
                  {
                      Symbol = p.Name,
                      Price = p.Value["price"].ToObject<double>()
                  })
                  .ToList();
    }

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

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

Then use it like this:

var quotes = JsonConvert.DeserializeObject(json, new QuoteListConverter());

Working demo: https://dotnetfiddle.net/kcU8DO

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