When you’re working with a JSON array, you can deserialize it to a list like this:
using System.Collections.Generic;
using System.Text.Json;
var movieList = JsonSerializer.Deserialize<List<Movie>>(json);
Code language: C# (cs)
This deserializes all of the objects in the JSON array into a List<Movie>. You can use this list object like usual.
Note: All examples will use System.Collections.Generic and System.Text.Json. I’ll exclude the using statements for brevity.
Table of Contents
Example – JSON array and code
Valid JSON is either an object (i.e. { }) or an array (i.e. [ ]). The following is an example of a JSON array that contains 10 movie objects:
[
{"Title":"Interstellar","Year":2014,"BoxOffice":701.8,"Director":"Christopher Nolan"},
{"Title":"Inception","Year":2010,"BoxOffice":836.8,"Director":"Christopher Nolan"},
{"Title":"Avengers: Endgame","Year":2019,"BoxOffice":2798,"Director":"Russo Brothers"},
{"Title":"The Social Network","Year":2010,"BoxOffice":224.9,"Director":"David Fincher"},
{"Title":"Seven","Year":1995,"BoxOffice":327.3,"Director":"David Fincher"},
{"Title":"Black Panther","Year":2018,"BoxOffice":1344,"Director":"Ryan Coogler"},
{"Title":"Edge of Tomorrow","Year":2014,"BoxOffice":370.5,"Director":"Doug Liman"},
{"Title":"Joker","Year":2019,"BoxOffice":333.7,"Director":"Todd Phillips"},
{"Title":"Avengers: Infinity War","Year":2018,"BoxOffice":2048,"Director":"Russo Brothers"},
{"Title":"Ford v Ferrari","Year":2019,"BoxOffice":225.5,"Director":"James Mangold"}
]
Code language: JSON / JSON with Comments (json)
Here’s an example of deserializing this JSON array into a list of movie objects (List<Movie>) and then using the list:
using System.Text.Json;
var list = JsonSerializer.Deserialize<List<Movie>>(moviesJson);
Console.WriteLine($"There are {list.Count} movies");
Code language: C# (cs)
This outputs the following:
There are 10 movies
Code language: plaintext (plaintext)
Deserialize and yield one object at a time
Deserialize<IEnumerable<Movie>> is the same as Deserialize<List<Movie>>. In both cases, it’ll deserialize all objects in the JSON array into List<Movie> and hold all objects in memory at once.
If you want to deserialize and yield one object at a time, use DeserializeAsyncEnumerable(). To use this, pass in the JSON as a stream:
using var movieJsonStream = new MemoryStream(Encoding.UTF8.GetBytes(moviesJson));
await foreach(var movie in JsonSerializer.DeserializeAsyncEnumerable<Movie>(movieJsonStream))
{
ProcessMovie(movie);
}
Code language: C# (cs)
Note: This example is converting a string into a MemoryStream. Try to use a stream directly when possible – such as reading a file as a stream, or reading the HTTP response stream.
Non-array collection of objects
Sometimes you’ll have to deal with collections of objects that are stored in a JSON object instead of in a JSON array. Here’s an example:
{
"Interstellar": {
"Year": 2014,
"BoxOffice": 701.8,
"Director": "Christopher Nolan"
},
"Inception": {
"Year": 2010,
"BoxOffice": 836.8,
"Director": "Christopher Nolan"
},
"Black Panther": {
"Year": 2018,
"BoxOffice": 1344,
"Director": "Ryan Coogler"
}
}
Code language: JSON / JSON with Comments (json)
This is a collection of movie objects, but it’s not a list. It’s a collection of key/value pairs. This can be deserialized into Dictionary<string, Movie>:
var movieMap = JsonSerializer.Deserialize<Dictionary<string, Movie>>(moviesJson);
Code language: C# (cs)
Keep it simple and deserialize to a class that matches the JSON structure. Add a new class to match the structure when necessary.
Newtonsoft example
Here’s how you deserialize to list with Newtonsoft (in case you aren’t using System.Text.Json):
using Newtonsoft.Json;
var movies = JsonConvert.DeserializeObject<List<Movie>>(moviesJson);
Console.WriteLine($"Average box office revenue = ${movies.Average(m => m.BoxOffice)} mil");
Code language: C# (cs)
Note: moviesJson is the movies JSON array from the Example – JSON array and code section.
This outputs:
Average box office revenue = $921.05 mil
Code language: plaintext (plaintext)
Hello,
Could you explain what the moviesJson is in
var movies = JsonConvert.DeserializeObject<List>(moviesJson);
Thank you!
Hi,
It’s using the movies JSON array shown in this section: Example – JSON array and code.
Thanks for asking this. I see I forgot to mention what JSON it’s using in the Newtonsoft example.
Having a small issue.
The deserialize works as expected and the is filled with the ten movies but if I try and drill into the Movie object they are all null.
Could you also post the .Net classes you used
I’d guess it’s either 1) non-public setters or 2) property name casing mismatch. Both of these would cause that.
Here’s the movie class I used:
public class Movie
{
public string Title { get; set; }
public int Year { get; set; }
public decimal BoxOffice { get; set; }
public string Director { get; set; }
}
Yes — that’s it. thanks for your help
You’re welcome, glad to help!
var movieList = JsonSerializer.Deserialize<List<Movie>>(json);
This line was very helpful for me, Thanks a lot
You’re welcome, I’m glad to hear this was helpful for you.
very good