How to query multiple json nodes?

Question

I have the following json:

{
  "key445" : {
    "text" : "cat",
    "id" : 445
  },
  "key457" : {
    "text" : "mouse",
    "id" : 457
  },
  "key458" : {
    "text" : "rodent",
    "id" : 458
  }
}

I am trying extract text and id into a List<TextIdentifier> (a class with string and an int), or even separately into List<string> and List<int>.

I read the text into JObject using JObject.Parse method. However, I can't figure out how to get to the text and id nodes. I've tried the following but it returns nothing.

var textTokens = o.SelectTokens("/*/text");
var idTokens = o.SelectTokens("/*/id");

How can I get to the tokens I want?

Any reason for parsing into a JObject rather than parsing into Dictionary<string, TextIdentifier> which I suspect would just work immediately? — Jon Skeet
– Jon Skeet, Commented Dec 10, 2020 at 18:51
@JonSkeet No reason, I just don't know how to do it. JObject seemed like a good way to debug this. — AngryHacker
– AngryHacker, Commented Dec 10, 2020 at 18:55
Right. So if TextIdentifier has writable properties for Text and Id, that's all you need to do :) — Jon Skeet
– Jon Skeet, Commented Dec 10, 2020 at 18:57
@JonSkeet My issue is finding the right JsonPath query to extract these tokens from json. Once I get them, I could definitely write them to an object. — AngryHacker
– AngryHacker, Commented Dec 10, 2020 at 19:01
My point is that you don't need to use JsonPath at all. Just convert the whole of your object to a Dictionary<string, TextIdentifier> and then if you only need the values, just use the Values property. Unless you need them in the order of the JSON file, which would be quite fragile. (Adding a sample now.) — Jon Skeet
– Jon Skeet, Commented Dec 10, 2020 at 19:05

Jon Skeet · Accepted Answer · 2020-12-10 19:09:32Z

2

I would just convert the whole JSON into a Dictionary<string, TextIdentifier> instead of trying to use JsonPath at all:

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

public class TextIdentifier
{
    public string Text { get; set; }
    public int Id { get; set; }
    public override string ToString() => $"Id: {Id}; Text: {Text}";
}

public class Test
{
    static void Main()
    {
        var json = File.ReadAllText("test.json");
        var dictionary = JsonConvert.DeserializeObject<Dictionary<string, TextIdentifier>>(json);

        foreach (var pair in dictionary)
        {
            Console.WriteLine($"{pair.Key} => {pair.Value}");
        }
    }
}

Output:

key445 => Id: 445; Text: cat
key457 => Id: 457; Text: mouse
key458 => Id: 458; Text: rodent

If you don't care about the keys, you can use dictionary.Values.ToList() to get a List<TextIdentifier> although you shouldn't rely on the order of them.

answered Dec 10, 2020 at 19:09

Jon Skeet

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1 Comment

AngryHacker Over a year ago

Wow, that is actually perfect. I wish I could upvote more.

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