Select JSON sub-node - json

Question

I am querying the Wikipedia API and am getting JSON back that looks like this:
https://en.wikipedia.org/w/api.php?action=query&prop=pageimages&titles=cessna%20172&pithumbsize=500&format=json
{"batchcomplete":"","query":{"normalized":[{"from":"cessna 172","to":"Cessna 172"}],"pages":{"173462":{"pageid":173462,"ns":0,"title":"Cessna 172","thumbnail":{"source":"https://upload.wikimedia.org/wikipedia/commons/thumb/a/ae/Cessna_172S_Skyhawk_SP%2C_Private_JP6817606.jpg/500px-Cessna_172S_Skyhawk_SP%2C_Private_JP6817606.jpg","width":500,"height":333},"pageimage":"Cessna_172S_Skyhawk_SP,_Private_JP6817606.jpg"}}}}
Using .Net Core 2.2, what is the proper way to get the image thumbnail out of this (the source property in this case)?

Answer 1

Parsing JSON is not a built in feature in .Net core 2.2 so you will want to add the Newtonsoft.Json package to the project with dotnet add package Newtonsoft.Json --version 12.0.3.
From there include Newtonsoft.Json by adding using Newtonsoft.Json.Linq; to the top of the file. and using System.Net; to use WebClient.
From there the code retrieves the string from the url. JObject.Parse parses the string as a JObject. We can get the property you want by chaining indexers: ["query"]["pages"]["173462"]["thumbnail"]["source"].
Full source:
using System;
using System.Net;
using Newtonsoft.Json.Linq;
class Program
{
static void Main(string[] args)
{
const string url = "https://en.wikipedia.org/w/api.php?action=query&prop=pageimages&titles=cessna%20172&pithumbsize=500&format=json";
using (WebClient client = new WebClient())
{
string rawString = client.DownloadString(url);
var jsonResult = JObject.Parse(rawString);
string thumbnail = jsonResult["query"]["pages"]["173462"]["thumbnail"]["source"];
Console.WriteLine(thumbnail);
}
}
}

Answer 2

Ideally, you will have to define a class and de-serialised the json. Example :
Batch batch = JsonConvert.DeserializeObject<Account>(json);
More details here.
However, at times, just to get one/two values, it might be overhead to use an entire class structure. In this case, a quick way might be to parse the json dynamically. Example which is taken from here:
public void JValueParsingTest()
{
var jsonString = #"{""Name"":""Rick"",""Company"":""West Wind"",
""Entered"":""2012-03-16T00:03:33.245-10:00""}";
dynamic json = JValue.Parse(jsonString);
// values require casting
string name = json.Name;
string company = json.Company;
DateTime entered = json.Entered;
Assert.AreEqual(name, "Rick");
Assert.AreEqual(company, "West Wind");
}