Json.Net Changing from JObject loops to JArray

Question

I'm pulling a JSON feed that looks like this.

{
    "bank": [
        {
            "id": 35,
            "name": "bank 1",
            "endpoints": [
                {
                    "epId": 407,
                    "epName": "FRED001"
                },
                {
                    "epId": 516,
                    "epName": "FRED002"
                },
                {
                    "epId": 625,
                    "epName": "FRED003"
                }
            ]
        },
        {
            "id": 32,
            "name": "bank 2",
            "endpoints": [
                {
                    "epId": 426,
                    "epName": "HENRY001"
                },
                {
                    "epId": 553,
                    "epName": "HENRY002"
                }
            ]
        },
        {
            "id": 20,
            "name": "bank 3",
            "endpoints": [
                {
                    "epId": 1802,
                    "epName": "GEORGE001"
                },
                {
                    "epId": 920,
                    "epName": "GEORGE002"
                },
                {
                    "epId": 1052,
                    "epName": "GEORGE003"
                }
            ]
        }
    ]
}

The end goal is to search using the known epName 'FRED001', and to retrieve the corresponding epId '407, output to a MessageBox.

I can do this in C# by using loops e.g:

JObject jResults = JObject.Parse(jsonfeed);
JToken jResults_bank = jResults["bank"];

foreach (JObject bank in Results_bank)
{
    JToken jResults_bank_endpoint = bank["endpoints"];
    foreach (JObject endpoint in jResults_bank_endpoint)
    {
        if (bank["epName"].ToString() == "FRED001")
                {
            MessageBow.Show(bank["epId"].ToString());
        }
    }
}

However this doesn't seem like the best way to do it and I'm convinced that I should be doing this in C# by building an array. How can I achieve the same outcome with a JArray?

Solution 1

There's no need to explicitly loop or change how you're parsing - you can just use LINQ with the JSON:

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

class Test
{
    static void Main(string[] args)
    {
        string text = File.ReadAllText("Test.json");
        JObject json = JObject.Parse(text);
        var ids = from bank in json["bank"]
                  from endpoint in bank["endpoints"]
                  where (string) endpoint["epName"] == "FRED001"
                  select (string) endpoint["epId"];
        foreach (var id in ids)
        {
            Console.WriteLine(id);
        }
    }
}

Solution 2

Or easy way would be to do just loop through it like this.

        JObject json = JObject.Parse(text);

        foreach (var id in json["bank"])
        {
           // your condition here
            if(id["epName"]=="FRED001")
            Console.WriteLine(id);
        }

Comments

[PhilH]

Wow, excellent. It's easy when you know how. Thanks. To extend this further, say I wanted to also retrieve "name": "bank 1", could I do this by editing the 'var ids'?

[PhilH]

Think I might have figured it out: var ids = from bank in json["bank"] from endpoint in bank["endpoints"] where (string) endpoint["epName"] == "FRED001" select new { epId = (string)endpoint["epId"], bankName = (string)bank["name"], }; foreach (var id in ids) { Console.WriteLine(id.epId); Console.WriteLine(id.bankName); }

[Jon Skeet]

@PhilH: Sorry, didn't see the edit to your comment - but yes, that's basically it.

[beast]

@JonSkeet performance-wise, lync query is better or using two for-loops?