parsing json w variable key-value pairs in c#

Question

I've got the following

 [
   {    
     "name": "ATVI",
     "dailyClosePrice": [
       {
         "3/15/2017": 210.08,
         "4/6/2017": 235.08,
         "4/21/2017": 243.61,
         "2/16/2017": 205.43
       }
     ]
   },
   {
    "name": "ADBE",
    "dailyClosePrice": [
      {
        "3/15/2017": 241.96,
        "4/6/2017": 270.22,
        "4/21/2017": 281.22,
        "2/16/2017": 225.26
      }
    ]
  }
]

The actual file has many more than 2, but you can see there are two of the main object here. I'm having trouble parsing the key-value pairs such as "3/15/2017": 210.08.

I need to make a class out of this, I guess an example class would have

class Stock
{
    public string Name{get;set;}
    public List<Entry> Prices{get;set;}
}

class Entry
{
    public string Date{get;set;}
    public double Price{get;set;}
}

So I'm trying to parse the file into a List

I guess I could use a StreamReader and use the Seek method to find a ":", but what I am having trouble with is then how to be able to only read in "ATVI". Once I get "ATVI" for example I set that string to a Name in a Stock, then can Seek for "{" and read in "3/15/2017" and set that to a Date in an Entry then Seek to a ":" and read in the double, etc.

If I do the above, I don't know how to read in select elements of the stream, in C#. In C# I mostly have read in strings that have a common spacing, usually I would use C for more complex things like here, but I am really hoping to use c# instead of C for this.

I don't care what method I need to use, I just want to read in the file.

If I had something like below, I would just use NewtonSoft

[
  {
    "name": "ATVI",
    "dailyClosePrice": [
      {"Date":"3/15/2017", "price":210.08}, 
      {"Date":"3/15/2017", "price": 210.08},
      {"Date":"4/6/2017", "price": 235.08},
      {"Date":"4/21/2017", "price": 243.61}
    ]
  },
  {
    "name": "ADBE",
    "dailyClosePrice": [
      {"Date":"3/15/2017", "price":210.08}, 
      {"Date":"3/15/2017", "price": 210.08},
      {"Date":"4/6/2017", "price": 235.08},
      {"Date":"4/21/2017", "price": 243.61}
    ]
  }
]

Why are you doing this manually and not just using a library that is specifically designed for the purpose and likely does it far better than you (or I) can? — DavidG, Jul 21 '17 at 21:32
I was using NewtonSoft for my other JSON files, but this one has a weird format — Devin Andres Salemi, Jul 21 '17 at 21:34
So I don't know how to do it even in a library, I will happily do it with a library, for now I just trying to do it myself rather than find a library, but if someone points out how to do it with a library would be fine — Devin Andres Salemi, Jul 21 '17 at 21:35
I just carefully fixed all the indentation, and even turned your pseudo-code into real code - why did you mess it up again? (If you want to add something, add it it to the *fixed* version...) — Jon Skeet, Jul 21 '17 at 21:42
Thank you, I apologize, I was editing at the same time, that is why, will try to see if I can find your edit again — Devin Andres Salemi, Jul 21 '17 at 21:44
I'll roll back your edit and add (and format...) the extra part — Jon Skeet, Jul 21 '17 at 21:47
(Please make more effort to format the post yourself in future though.) — Jon Skeet, Jul 21 '17 at 21:49

score 5 · Accepted Answer · answered Jul 21 '17 at 21:46

You definitely shouldn't be parsing this by hand - Json.NET will be absolutely fine with this, so long as you model it correctly. The JSON represents a list of objects, each of which has a name (string) and a dailyClosePrice which appears to be a list which always has a single value, which is in turn an object mapping dates to prices. You can represent that fairly easily:

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

public class Stock
{
    public string Name { get; set; }
    public List<Dictionary<string, decimal>> DailyClosePrice { get; set; }
}

class Test
{
    static void Main(string[] args)
    {
        string json = File.ReadAllText("test.json");
        var stocks = JsonConvert.DeserializeObject<List<Stock>>(json);

        foreach (var stock in stocks)
        {
            Console.WriteLine($"Name: {stock.Name}");
            Console.WriteLine("Prices:");
            // Assume there's only ever a single entry, at least for now...
            var prices = stock.DailyClosePrice.Single();
            // TODO: Parse the (ugly, US-based) date format...
            var entries = prices.Select(kvp => new { Date = kvp.Key, Price = kvp.Value });
            foreach (var entry in entries)
            {
                Console.WriteLine($"  {entry.Date}: {entry.Price}");
            }
        }
    }
}

Now that Stock class is pretty ugly, but it represents what's in the JSON - it should then be easy enough to convert that representation into a more palatable one for the rest of your code.

Thank you very much :) I am wondering if you happen to know where I could read up on (kvp => new { Date = kvp.Key, Price = kvp.Value }) I use expressions like this sometimes, but wish I had a deeper understanding on exactly what goes on — Devin Andres Salemi, Jul 21 '17 at 22:15
@DevinAndresSalemi: Find a good LINQ tutorial, basically. (Or my book, C# in Depth, of course :) — Jon Skeet, Jul 21 '17 at 22:16
@jonskeet why did you say this: "ugly, US-based" i am really curious. Dont worry i am not a politician and neither are you so ai wont hold it against you ;) but you must have a valid reason. — CodingYoshi, Jul 22 '17 at 07:31
@CodingYoshi: The US date format is ridiculous, in terms of being month/year/day. It either goes from smallest to largest, nor largest to smallest. The format used by much of the rest of the world (day/month/year) is definitely unpleasant in terms of not being naturally sortable, and not like other numeric representations (where left-most=most-significant) but at least it goes in one direction. For a machine-readable format like JSON, ISO-8601 is a much better choice IMO. Putting the year first makes it *unambiguously* ISO-8601 (as no-one uses year-day-month). — Jon Skeet, Jul 22 '17 at 07:35

CodingYoshi · Answer 2 · 2017-07-21T22:20:26.287

1

You can always create C# classes for your JSON using this technique.

You need the following classes for your JSON:

public class Stock
{
    public string Name { get; set; }
    public IEnumerable<IDictionary<DateTime, float>> DailyClosePrice { get; set; }
}

Download JSON.NET library (it is available as NuGet package). Then use the library like this and you are done:

var stocks = JsonConvert.DeserializeObject<List<Stock>>("YourJSON");

edited Jul 21 '17 at 22:20

answered Jul 21 '17 at 22:01

CodingYoshi

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Except that isn't using `DailyClosePice` (sic) at all, and the value in your dictionary is a `string` instead of a numeric one... – Jon Skeet Jul 21 '17 at 22:16
I wouldn't personally use `DateTime` as the key there - better to do the parsing directly, given that it's in a very specific format (which may not be the default culture's format). I'd also recommend against using `float` for currency values. (Although as it's a numeric value in JSON, it's already probably going to be treated as `double` on many platforms...) – Jon Skeet Jul 21 '17 at 22:33
@JonSkeet Point well taken-especially about date parsing. thanks. – CodingYoshi Jul 21 '17 at 23:55

parsing json w variable key-value pairs in c#

2 Answers2