json.md

Working with JSON in C#

System.Text.Json is a modern built-in alternative to Newtonsoft libraries.

using System.Text.Json;

Download JSON

private static JsonDocument RequestJson(string url) => RequestJsonAsync(url).Result;

private static async Task<JsonDocument> RequestJsonAsync(string url)
{
    using HttpClient client = new();
    using HttpResponseMessage response = await client.GetAsync(url);
    using HttpContent content = response.Content;
    string json = await content.ReadAsStringAsync();
    return JsonDocument.Parse(json);
}

Create JSON From Scratch

using MemoryStream stream = new();
JsonWriterOptions options = new() { Indented = true };
using Utf8JsonWriter writer = new(stream, options);

writer.WriteStartObject();
writer.WriteNumber("simple value", 123);
writer.WriteStartArray("more values");
for (int i = 0; i < 10; i++)
{
    writer.WriteStartObject();
    writer.WriteString("alpha", $"asdf{i}");
    writer.WriteNumber("beta", i);
    writer.WriteEndObject();
}
writer.WriteEndArray();
writer.WriteEndObject();

writer.Flush();
string json = Encoding.UTF8.GetString(stream.ToArray());

Navigate JSON Manually

using JsonDocument document = JsonDocument.Parse(File.ReadAllText(JSON_FILE));

string version = document.RootElement.GetProperty("version").GetString();
string generated = document.RootElement.GetProperty("generated").GetString();

foreach (JsonElement recipeElement in document.RootElement.GetProperty("recipes").EnumerateArray())
{
    string id = recipeElement.GetProperty("id").GetString();
    string category = recipeElement.GetProperty("category").GetString();
    string title = recipeElement.GetProperty("title").GetString();
    string description = recipeElement.GetProperty("description").GetString();
    string code = recipeElement.GetProperty("code").GetString();
}

using (JsonDocument document = JsonDocument.Parse(jsonString))
{
    double temperatureC = document.RootElement.GetProperty("temperatureC").GetDouble();
    List<Ion> ions = new List<Ion>();
    foreach (JsonElement element in document.RootElement.GetProperty("ions").EnumerateArray())
    {
        string name = element.GetProperty("name").GetString();
        int charge = element.GetProperty("charge").GetInt32();
        double conductivity = element.GetProperty("conductivity").GetDouble();
    }
};

Serialize/Deserialize C# Objects To/From JSON

Serializable objects are POCOs that:

• Have auto-properties
• Have a parameterless constructor

class Life
{
    public string Name { get; set; }
    public int Age { get; set; }
    public List<string> Interests { get; set; } = new List<string>();
}

// instantiate an object
Life myLife = new Life() { Name = "Scott", Age = 35 };
myLife.Interests.Add("science");
myLife.Interests.Add("computers");
myLife.Interests.Add("space");

// C# Object to JSON (with option for pretty formatting)
var options = new JsonSerializerOptions() { WriteIndented = true };
string json = JsonSerializer.Serialize(myLife, options);
Console.WriteLine(json);

// JSON to C# object
Life myNewLife = JsonSerializer.Deserialize<Life>(json);
Console.WriteLine(myNewLife.Name + " likes " + string.Join(" and ", myNewLife.Interests));

Prettify JSON with C#

// convert an ugly document to a pretty one
JsonDocument document = JsonDocument.Parse(jsonString);
using var stream = new MemoryStream();
var options = new JsonWriterOptions() { Indented = true };
using var writer = new Utf8JsonWriter(stream, options);
document.WriteTo(writer);
writer.Flush();
string jsonPretty = Encoding.UTF8.GetString(stream.ToArray());