Iterate Through JSON Array in C#

Question

I'm trying to figure out how to loop through some JSON data to insert it into a DataGrid, to serve as an event log. However trying to parse JSON is giving me a headache.

I'm trying to use JSON.NET by Newtonsoft.

The JSON string looks something like this;

{
    "result" : "ok",
    "response" : {
    "first" : 0,
    "count" : 190,
    "now" : 1509822169,
    "events" : [
    {
        "index" : 0,
        "time" : 1509815973,
        "name" : "SessionCreated",
        "attributes" : {}
    },
    {
        "index" : 1,
        "time" : 1509815973,
        "name" : "PlayerJoined",
        "refid" : 32896,
        "attributes" : {}
        "Name" : "Dealman",
        "SteamId" : "76561197986562417"
    },
    {
        "index" : 2,
        "time" : 1509815973,
        "name" : "Authenticated",
        "refid" : 32896,
        "attributes" : {}
    },
    {
        "index" : 3,
        "time" : 1509815973,
        "name" : "StateChanged",
        "attributes" : {}
        "PreviousState" : "None",
        "NewState" : "Lobby"
    },
    {
        "index" : 4,
        "time" : 1509815998,
        "name" : "PlayerChat",
        "refid" : 32896,
        "attributes" : {
            "Message" : "This is a message"
        }
    },
    {
        "index" : 5,
        "time" : 1509816030,
        "name" : "StateChanged",
        "attributes" : {}
        "PreviousState" : "Lobby",
        "NewState" : "Loading"
    },
    {
        "index" : 6,
        "time" : 1509816030,
        "name" : "SessionSetup",
        "attributes" : {}
        "GridSize" : 22,
        "MaxPlayers" : 22,
        "PracticeLength" : 0,
        "QualifyLength" : 15,
        "RaceLength" : 6,
        "Flags" : -1316224232,
        "TrackId" : -52972612,
        "GameMode" : -1958878043
    },
    {
        "index" : 7,
        "time" : 1509816030,
        "name" : "StageChanged",
        "attributes" : {
            "PreviousStage" : "Practice1",
            "NewStage" : "Qualifying1",
            "Length" : 15
        }
    },
    {
        "index" : 8,
        "time" : 1509816046,
        "name" : "StateChanged",
        "attributes" : {
            "PreviousState" : "Loading",
            "NewState" : "Race"
        }
    },
    {
        "index" : 9,
        "time" : 1509816046,
        "name" : "ParticipantCreated",
        "refid" : 32896,
        "participantid" : 0,
        "attributes" : {
            "Name" : "Dealman",
            "IsPlayer" : 1,
            "VehicleId" : 1764851930,
            "LiveryId" : 54
        }
    }]}
}

I've been trying to do something like this;

dynamic jsonObj = JsonConvert.DeserializeObject(messageContent);
foreach(var item in jsonObj)
{
    Trace.WriteLine(item.result);
}

I've also tried some other methods like using lists, but I simply can't get it to work and I keep getting a RuntimeBinderException. I've been stuck at this for so long now that I'm starting to consider to just use regex as this seems to be more work than it's worth.

What am I missing and/or misunderstanding here? :(

archnae · Accepted Answer · 2017-11-04 21:30:01Z

1

   public static ExpandoObject ToExpando(string json)
    {
        if (string.IsNullOrEmpty(json))
            return null;
        return (ExpandoObject)ToExpandoObject(JToken.Parse(json));
    }


    private static object ToExpandoObject(JToken token)
    {

        switch (token.Type)
        {
            case JTokenType.Object:
                var expando = new ExpandoObject();
                var expandoDic = (IDictionary<string, object>)expando;
                foreach(var prop in token.Children<JProperty>())
                    expandoDic.Add(prop.Name, ToExpandoObject(prop.Value));
                return expando;
            case JTokenType.Array:
                return token.Select(ToExpandoObject).ToList();

            default:
                return ((JValue)token).Value;
        }
    }

    var ebj = ToExpando(json);
    var name = (ebj as dynamic).response.events[1].name;

A better (easier to use) version using dynamic.

answered Nov 4, 2017 at 21:30

archnae

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1 Comment

Dealman Over a year ago

Oooh, very nice! And here I thought I was just gonna be best of "bruteforcing" my way using SelectToken... Will do some more testing but it seems to work nicely so far! Thanks a bunch

archnae · Accepted Answer · 2017-11-04 20:14:53Z

1

    var json = @"...";

    var obj = ToObject(json) as IDictionary<string, object>;
    var resp = obj["response"] as IDictionary<string, object>;
    var events = resp["events"];

    public static object ToObject(string json)
    {
        if (string.IsNullOrEmpty(json))
            return null;
        return ToObject(JToken.Parse(json));
    }

    private static object ToObject(JToken token)
    {
        switch (token.Type)
        {
            case JTokenType.Object:
                return token.Children<JProperty>()
                            .ToDictionary(prop => prop.Name,
                                          prop => ToObject(prop.Value),
                                          StringComparer.OrdinalIgnoreCase);

            case JTokenType.Array:
                return token.Select(ToObject).ToList();

            default:
                return ((JValue)token).Value;
        }
    }

The json string is converted to a Dictionary where items are simple values, lists or nested dictionaries. Much easier to iterate on dictionaries than use reflection.

BTW, there is a bug in your json - missing comma after "attributes" : {}. Also, having both "name" and "Name" as properties is not a good idea.

edited Nov 4, 2017 at 20:14

answered Nov 4, 2017 at 19:54

archnae

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1 Comment

Dealman Over a year ago

Thanks! As for the missing comma - is it necessary though since it's the last entry in the array? Also, the HTTP API that return this data is embedded into the game. Thus I am unfortunately unable to make any changes to it. I've added your code and I'm trying to figure out how it works. Looping through resp["events"] gives me this; [first, 0] [count, 302] [now, 1509826920] [events, System.Collections.Generic.List`1[System.Object]]

John H · Accepted Answer · 2017-11-04 20:41:45Z

1

The problem you're having is because result is a top-level property that isn't part of a collection, so trying to access it using a loop doesn't make any sense. This prints ok as expected:

using Newtonsoft.Json;
using System;
using System.IO;

namespace SO47114632Core
{
    class Program
    {
        static void Main(string[] args)
        {
            var content = File.ReadAllText("test.json");
            dynamic json = JsonConvert.DeserializeObject(content);
            Console.WriteLine(json.result);
        }
    }
}

I added test.json, with the JSON from your question, in the root folder of the project, setting Copy to Output Directory to Always in the file's properties:

edited Nov 4, 2017 at 20:41

answered Nov 4, 2017 at 20:27

John H

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7 Comments

Dealman Over a year ago

For me it returns 2 errors, am I missing some references or something perhaps? Exception thrown: 'Microsoft.CSharp.RuntimeBinder.RuntimeBinderException' in System.Core.dll Exception thrown: 'Microsoft.CSharp.RuntimeBinder.RuntimeBinderException' in mscorlib.dll

John H Over a year ago

@Dealman I've tried with both a normal console app and a .NET Core console app, and both are working correctly for me. In fact, the code is identical, so I'll edit my answer to provide the full program.

John H Over a year ago

@Dealman Done. If you're still having problems, I'd recommend creating a fresh solution and trying out the above. If that works, you know it's something else to do with your current project.

Dealman Over a year ago

I'm sure it works, I'm just not quite sure what the RuntimeBinderException means - it doesn't really tell me much. You reckon it might be because I do this in an async task? Or inside a using statement?

Dealman Over a year ago

string test = json.result; Trace.WriteLine(test); Doing it like that works. I guess Trace.WriteLine works a fair bit differently than Console.WriteLine under the hood?

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